-A flag

If you previously used "Configure -Dsitelib" or "-Dsitearch" to set special values for library directories, you might wish to consider using the new "-Dsiteprefix" setting instead. Also, if you wish to re-use a config.sh file from an earlier version of perl, you should be sure to check that Configure makes sensible choices for the new directories. See INSTALL for complete details.

*

The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread extension.

*

GNU/Hurd is now supported.

*

Rhapsody/Darwin is now supported.

*

EPOC is now supported (on Psion 5).

*

The cygwin port (formerly cygwin32) has been greatly improved.

DOS

*

Perl now works with djgpp 2.02 (and 2.03 alpha).

*

Environment variable names are not converted to uppercase any more.

*

Incorrect exit codes from backticks have been fixed.

*

This port continues to use its own builtin globbing (not File::Glob).

OS390 (OpenEdition MVS)

It is unclear whether future versions will renew support for this platform, but the possibility exists.

VMS

Expand %ENV-handling code to allow runtime mapping to logical names, CLI symbols, and CRTL environ array.

Extension of subprocess invocation code to accept filespecs as command ``verbs''.

Add to Perl command line processing the ability to use default file types and to recognize Unix-style "2>&1".

Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS.

Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly.

Barewords at start of Unix-syntax paths may be treated as text rather than only as logical names.

Optional secure translation of several logical names used internally by Perl.

Miscellaneous bugfixing and porting of new core code to VMS.

Thanks are gladly extended to the many people who have contributed VMS patches, testing, and ideas.

When given a pathname that consists only of a drivename, such as "A:", opendir() and stat() now use the current working directory for the drive rather than the drive root.

The builtin XSUB functions in the Win32:: namespace are documented. See Win32.

$^X now contains the full path name of the running executable.

A Win32::GetLongPathName() function is provided to complement Win32::GetFullPathName() and Win32::GetShortPathName(). See Win32.

POSIX::uname() is supported.

system(1,...) now returns true process IDs rather than process handles. kill() accepts any real process id, rather than strictly return values from system(1,...).

For better compatibility with Unix, "kill(0, $pid)" can now be used to test whether a process exists.

The "Shell" module is supported.

Better support for building Perl under command.com in Windows 95 has been added.

Scripts are read in binary mode by default to allow ByteLoader (and the filter mechanism in general) to work properly. For compatibility, the DATA filehandle will be set to text mode if a carriage return is detected at the end of the line containing the __END__ or __DATA__ token; if not, the DATA filehandle will be left open in binary mode. Earlier versions always opened the DATA filehandle in text mode.

The glob() operator is implemented via the "File::Glob" extension, which supports glob syntax of the C shell. This increases the flexibility of the glob() operator, but there may be compatibility issues for programs that relied on the older globbing syntax. If you want to preserve compatibility with the older syntax, you might want to run perl with "-MFile::DosGlob". For details and compatibility information, see File::Glob.

<HANDLE> on empty files

This means that the following will append ``foo'' to an empty file (it used to do nothing):

    perl -0777 -pi -e 's/^/foo/' empty_file

The behaviour of:

    perl -pi -e 's/^/foo/' empty_file

is unchanged (it continues to leave the file empty).

Lexical lookups for variables appearing in "eval '...'" within functions that were themselves called within an "eval '...'" were searching the wrong place for lexicals. The lexical search now correctly ends at the subroutine's block boundary.

The use of "return" within "eval {...}" caused $@ not to be reset correctly when no exception occurred within the eval. This has been fixed.

Parsing of here documents used to be flawed when they appeared as the replacement expression in "eval 's/.../.../e'". This has been fixed.

The mechanism for reporting such errors has been reimplemented to queue compile-time errors and report them at the end of the compilation as true errors rather than as warnings. This fixes cases where error messages leaked through in the form of warnings when code was compiled at run time using "eval STRING", and also allows such errors to be reliably trapped using "eval "..."".

The new behavior is to produce an empty list if (and only if) the original list was empty. Consider the following example:

    @a = (1,undef,undef,2)[2,1,2];

The old behavior would have resulted in @a having no elements. The new behavior ensures it has three undefined elements.

Note in particular that the behavior of slices of the following cases remains unchanged:

    @a = ()[1,2];
    @a = (getpwent)[7,0];
    @a = (anything_returning_empty_list())[2,1,2];
    @a = @b[2,1,2];
    @a = @c{'a','b','c'};

See perldata.

(\$) prototype and $foo{a}

goto &sub and AUTOLOAD

-bareword allowed under use integer

Failures in DESTROY()

Numbers formatted according to the local numeric locale (such as using a decimal comma instead of a decimal dot) caused ``isn't numeric'' warnings, even while the operations accessing those numbers produced correct results. These warnings have been discontinued.

Operations that aren't filehandle constructors used to leak memory when used on invalid filehandles. This has been fixed.

Constructs that modified @_ could fail to deallocate values in @_ and thus leak memory. This has been corrected.

END blocks and the -c switch

See ``Support for CHECK blocks'' for how to run things when the compile phase ends.

Potential to leak DATA filehandles

This caveat is now better explained in the documentation. See perldata.

%s variable %s masks earlier declaration in same %s

(W misc) A ``my'' or ``our'' variable has been redeclared in the current scope or statement, effectively eliminating all access to the previous instance. This is almost always a typographical error. Note that the earlier variable will still exist until the end of the scope or until all closure referents to it are destroyed.

my sub not yet implemented

(F) Lexically scoped subroutines are not yet implemented. Don't try that yet.

our variable %s redeclared

(W misc) You seem to have already declared the same global once before in the current lexical scope.

'!' allowed only after types %s

(F) The '!' is allowed in pack() and unpack() only after certain types. See ``pack'' in perlfunc.

/ cannot take a count

(F) You had an unpack template indicating a counted-length string, but you have also specified an explicit size for the string. See ``pack'' in perlfunc.

/ must be followed by a, A or Z

(F) You had an unpack template indicating a counted-length string, which must be followed by one of the letters a, A or Z to indicate what sort of string is to be unpacked. See ``pack'' in perlfunc.

/ must be followed by a*, A* or Z*

(F) You had a pack template indicating a counted-length string, Currently the only things that can have their length counted are a*, A* or Z*. See ``pack'' in perlfunc.

/ must follow a numeric type

(F) You had an unpack template that contained a '#', but this did not follow some numeric unpack specification. See ``pack'' in perlfunc.

/%s/: Unrecognized escape \\%c passed through

(W regexp) You used a backslash-character combination which is not recognized by Perl. This combination appears in an interpolated variable or a "'"-delimited regular expression. The character was understood literally.

/%s/: Unrecognized escape \\%c in character class passed through

(W regexp) You used a backslash-character combination which is not recognized by Perl inside character classes. The character was understood literally.

/%s/ should probably be written as %s

(W syntax) You have used a pattern where Perl expected to find a string, as in the first argument to "join". Perl will treat the true or false result of matching the pattern against $_ as the string, which is probably not what you had in mind.

%s() called too early to check prototype

(W prototype) You've called a function that has a prototype before the parser saw a definition or declaration for it, and Perl could not check that the call conforms to the prototype. You need to either add an early prototype declaration for the subroutine in question, or move the subroutine definition ahead of the call to get proper prototype checking. Alternatively, if you are certain that you're calling the function correctly, you may put an ampersand before the name to avoid the warning. See perlsub.

%s argument is not a HASH or ARRAY element

(F) The argument to exists() must be a hash or array element, such as:

    $foo{$bar}
    $ref->{"susie"}[12]

%s argument is not a HASH or ARRAY element or slice

(F) The argument to delete() must be either a hash or array element, such as:

    $foo{$bar}
    $ref->{"susie"}[12]

or a hash or array slice, such as:

    @foo[$bar, $baz, $xyzzy]
    @{$ref->[12]}{"susie", "queue"}

%s argument is not a subroutine name

(F) The argument to exists() for "exists &sub" must be a subroutine name, and not a subroutine call. "exists &sub()" will generate this error.

%s package attribute may clash with future reserved word: %s

(W reserved) A lowercase attribute name was used that had a package-specific handler. That name might have a meaning to Perl itself some day, even though it doesn't yet. Perhaps you should use a mixed-case attribute name, instead. See attributes.

(in cleanup) %s

(W misc) This prefix usually indicates that a DESTROY() method raised the indicated exception. Since destructors are usually called by the system at arbitrary points during execution, and often a vast number of times, the warning is issued only once for any number of failures that would otherwise result in the same message being repeated.

Failure of user callbacks dispatched using the "G_KEEPERR" flag could also result in this warning. See ``G_KEEPERR'' in perlcall.

<> should be quotes

(F) You wrote "require <file>" when you should have written "require 'file'".

Attempt to join self

(F) You tried to join a thread from within itself, which is an impossible task. You may be joining the wrong thread, or you may need to move the join() to some other thread.

Bad evalled substitution pattern

(F) You've used the /e switch to evaluate the replacement for a substitution, but perl found a syntax error in the code to evaluate, most likely an unexpected right brace '}'.

Bad realloc() ignored

(S) An internal routine called realloc() on something that had never been malloc()ed in the first place. Mandatory, but can be disabled by setting environment variable "PERL_BADFREE" to 1.

Bareword found in conditional

(W bareword) The compiler found a bareword where it expected a conditional, which often indicates that an || or && was parsed as part of the last argument of the previous construct, for example:

    open FOO || die;

It may also indicate a misspelled constant that has been interpreted as a bareword:

    use constant TYPO => 1;
    if (TYOP) { print "foo" }

The "strict" pragma is useful in avoiding such errors.

Binary number > 0b11111111111111111111111111111111 non-portable

(W portable) The binary number you specified is larger than 2**32-1 (4294967295) and therefore non-portable between systems. See perlport for more on portability concerns.

Bit vector size > 32 non-portable

(W portable) Using bit vector sizes larger than 32 is non-portable.

Buffer overflow in prime_env_iter: %s

(W internal) A warning peculiar to VMS. While Perl was preparing to iterate over %ENV, it encountered a logical name or symbol definition which was too long, so it was truncated to the string shown.

Can't check filesystem of script %s

(P) For some reason you can't check the filesystem of the script for nosuid.

Can't declare class for non-scalar %s in %s

(S) Currently, only scalar variables can declared with a specific class qualifier in a ``my'' or ``our'' declaration. The semantics may be extended for other types of variables in future.

Can't declare %s in %s

(F) Only scalar, array, and hash variables may be declared as ``my'' or ``our'' variables. They must have ordinary identifiers as names.

Can't ignore signal CHLD, forcing to default

(W signal) Perl has detected that it is being run with the SIGCHLD signal (sometimes known as SIGCLD) disabled. Since disabling this signal will interfere with proper determination of exit status of child processes, Perl has reset the signal to its default value. This situation typically indicates that the parent program under which Perl may be running (e.g., cron) is being very careless.

Can't modify non-lvalue subroutine call

(F) Subroutines meant to be used in lvalue context should be declared as such, see ``Lvalue subroutines'' in perlsub.

Can't read CRTL environ

(S) A warning peculiar to VMS. Perl tried to read an element of %ENV from the CRTL's internal environment array and discovered the array was missing. You need to figure out where your CRTL misplaced its environ or define PERL_ENV_TABLES (see perlvms) so that environ is not searched.

Can't remove %s: %s, skipping file

(S) You requested an inplace edit without creating a backup file. Perl was unable to remove the original file to replace it with the modified file. The file was left unmodified.

Can't return %s from lvalue subroutine

(F) Perl detected an attempt to return illegal lvalues (such as temporary or readonly values) from a subroutine used as an lvalue. This is not allowed.

Can't weaken a nonreference

(F) You attempted to weaken something that was not a reference. Only references can be weakened.

Character class [:%s:] unknown

(F) The class in the character class [: :] syntax is unknown. See perlre.

Character class syntax [%s] belongs inside character classes

(W unsafe) The character class constructs [: :], [= =], and [. .] go inside character classes, the [] are part of the construct, for example: /[012[:alpha:]345]/. Note that [= =] and [. .] are not currently implemented; they are simply placeholders for future extensions.

Constant is not %s reference

(F) A constant value (perhaps declared using the "use constant" pragma) is being dereferenced, but it amounts to the wrong type of reference. The message indicates the type of reference that was expected. This usually indicates a syntax error in dereferencing the constant value. See ``Constant Functions'' in perlsub and constant.

constant(%s): %s

(F) The parser found inconsistencies either while attempting to define an overloaded constant, or when trying to find the character name specified in the "\N{...}" escape. Perhaps you forgot to load the corresponding "overload" or "charnames" pragma? See charnames and overload.

CORE::%s is not a keyword

(F) The CORE:: namespace is reserved for Perl keywords.

defined(@array) is deprecated

(D) defined() is not usually useful on arrays because it checks for an undefined scalar value. If you want to see if the array is empty, just use "if (@array) { # not empty }" for example.

defined(%hash) is deprecated

(D) defined() is not usually useful on hashes because it checks for an undefined scalar value. If you want to see if the hash is empty, just use "if (%hash) { # not empty }" for example.

Did not produce a valid header

See Server error.

(Did you mean local instead of our?)

(W misc) Remember that ``our'' does not localize the declared global variable. You have declared it again in the same lexical scope, which seems superfluous.

Document contains no data

See Server error.

entering effective %s failed

(F) While under the "use filetest" pragma, switching the real and effective uids or gids failed.

false [] range %s in regexp

(W regexp) A character class range must start and end at a literal character, not another character class like "\d" or "[:alpha:]". The ``-'' in your false range is interpreted as a literal ``-''. Consider quoting the ``-'', ``\-''. See perlre.

Filehandle %s opened only for output

(W io) You tried to read from a filehandle opened only for writing. If you intended it to be a read/write filehandle, you needed to open it with ``+<'' or ``+>'' or ``+>>'' instead of with ``<'' or nothing. If you intended only to read from the file, use ``<''. See ``open'' in perlfunc.

flock() on closed filehandle %s

(W closed) The filehandle you're attempting to flock() got itself closed some time before now. Check your logic flow. flock() operates on filehandles. Are you attempting to call flock() on a dirhandle by the same name?

Global symbol %s requires explicit package name

(F) You've said ``use strict vars'', which indicates that all variables must either be lexically scoped (using ``my''), declared beforehand using ``our'', or explicitly qualified to say which package the global variable is in (using ``::'').

Hexadecimal number > 0xffffffff non-portable

(W portable) The hexadecimal number you specified is larger than 2**32-1 (4294967295) and therefore non-portable between systems. See perlport for more on portability concerns.

Ill-formed CRTL environ value %s

(W internal) A warning peculiar to VMS. Perl tried to read the CRTL's internal environ array, and encountered an element without the "=" delimiter used to separate keys from values. The element is ignored.

Ill-formed message in prime_env_iter: |%s|

(W internal) A warning peculiar to VMS. Perl tried to read a logical name or CLI symbol definition when preparing to iterate over %ENV, and didn't see the expected delimiter between key and value, so the line was ignored.

Illegal binary digit %s

(F) You used a digit other than 0 or 1 in a binary number.

Illegal binary digit %s ignored

(W digit) You may have tried to use a digit other than 0 or 1 in a binary number. Interpretation of the binary number stopped before the offending digit.

Illegal number of bits in vec

(F) The number of bits in vec() (the third argument) must be a power of two from 1 to 32 (or 64, if your platform supports that).

Integer overflow in %s number

(W overflow) The hexadecimal, octal or binary number you have specified either as a literal or as an argument to hex() or oct() is too big for your architecture, and has been converted to a floating point number. On a 32-bit architecture the largest hexadecimal, octal or binary number representable without overflow is 0xFFFFFFFF, 037777777777, or 0b11111111111111111111111111111111 respectively. Note that Perl transparently promotes all numbers to a floating point representation internally---subject to loss of precision errors in subsequent operations.

Invalid %s attribute: %s

The indicated attribute for a subroutine or variable was not recognized by Perl or by a user-supplied handler. See attributes.

Invalid %s attributes: %s

The indicated attributes for a subroutine or variable were not recognized by Perl or by a user-supplied handler. See attributes.

invalid [] range %s in regexp

The offending range is now explicitly displayed.

Invalid separator character %s in attribute list

(F) Something other than a colon or whitespace was seen between the elements of an attribute list. If the previous attribute had a parenthesised parameter list, perhaps that list was terminated too soon. See attributes.

Invalid separator character %s in subroutine attribute list

(F) Something other than a colon or whitespace was seen between the elements of a subroutine attribute list. If the previous attribute had a parenthesised parameter list, perhaps that list was terminated too soon.

leaving effective %s failed

(F) While under the "use filetest" pragma, switching the real and effective uids or gids failed.

Lvalue subs returning %s not implemented yet

(F) Due to limitations in the current implementation, array and hash values cannot be returned in subroutines used in lvalue context. See ``Lvalue subroutines'' in perlsub.

Method %s not permitted

See Server error.

Missing %sbrace%s on \N{}

(F) Wrong syntax of character name literal "\N{charname}" within double-quotish context.

Missing command in piped open

(W pipe) You used the "open(FH, "| command")" or "open(FH, "command |")" construction, but the command was missing or blank.

Missing name in my sub

(F) The reserved syntax for lexically scoped subroutines requires that they have a name with which they can be found.

No %s specified for -%c

(F) The indicated command line switch needs a mandatory argument, but you haven't specified one.

No package name allowed for variable %s in our

(F) Fully qualified variable names are not allowed in ``our'' declarations, because that doesn't make much sense under existing semantics. Such syntax is reserved for future extensions.

No space allowed after -%c

(F) The argument to the indicated command line switch must follow immediately after the switch, without intervening spaces.

no UTC offset information; assuming local time is UTC

(S) A warning peculiar to VMS. Perl was unable to find the local timezone offset, so it's assuming that local system time is equivalent to UTC. If it's not, define the logical name SYS$TIMEZONE_DIFFERENTIAL to translate to the number of seconds which need to be added to UTC to get local time.

Octal number > 037777777777 non-portable

(W portable) The octal number you specified is larger than 2**32-1 (4294967295) and therefore non-portable between systems. See perlport for more on portability concerns.

See also perlport for writing portable code.

panic: del_backref

(P) Failed an internal consistency check while trying to reset a weak reference.

panic: kid popen errno read

(F) forked child returned an incomprehensible message about its errno.

panic: magic_killbackrefs

(P) Failed an internal consistency check while trying to reset all weak references to an object.

Parentheses missing around %s list

(W parenthesis) You said something like

    my $foo, $bar = @_;

when you meant

    my ($foo, $bar) = @_;

Remember that ``my'', ``our'', and ``local'' bind tighter than comma.

Possible unintended interpolation of %s in string

(W ambiguous) It used to be that Perl would try to guess whether you wanted an array interpolated or a literal @. It no longer does this; arrays are now always interpolated into strings. This means that if you try something like:

        print "
and the array @example doesn't exist, Perl is going to
print "fred.com", which is probably not what you wanted.
To get a literal "@" sign in a string, put a backslash
before it, just as you would to get a literal "$" sign.
Possible Y2K bug: %s
 (W y2k) You are concatenating the number
19 with another number, which could be a potential Year 2000
problem.
pragma attrs is deprecated, use sub NAME
: ATTRS instead
 (W deprecated) You have written something
like this:
    sub doit
    {
        use attrs qw(locked);
    }
You should use the new declaration syntax instead.
    sub doit : locked
    {
        ...
The "use attrs" pragma is now obsolete, and is only
provided for backward-compatibility. See ``Subroutine Attributes''
in perlsub.
Premature end of script headers
 See Server error.
Repeat count in pack overflows
 (F) You can't specify a repeat count so
large that it overflows your signed integers. See ``pack'' in
perlfunc.
Repeat count in unpack overflows
 (F) You can't specify a repeat count so
large that it overflows your signed integers. See ``unpack'' in
perlfunc.
realloc() of freed memory ignored
 (S) An internal routine called
realloc() on something that had already been freed.
Reference is already weak
 (W misc) You have attempted to weaken a
reference that is already weak. Doing so has no effect.
setpgrp can't take arguments
 (F) Your system has the setpgrp()
from BSD 4.2, which takes no arguments,
unlike POSIX setpgid(), which takes a
process ID and process group ID.
Strange *+?{} on zero-length expression
 (W regexp) You applied a regular
expression quantifier in a place where it makes no sense, such as
on a zero-width assertion. Try putting the quantifier inside the
assertion instead. For example, the way to match ``abc'' provided
that it is followed by three repetitions of ``xyz'' is
"/abc(?=(?:xyz){3})/", not "/abc(?=xyz){3}/".
switching effective %s is not implemented
 (F) While under the "use
filetest" pragma, we cannot switch the real and effective uids
or gids.
This Perl can't reset CRTL environ
elements (%s)

This Perl can't set CRTL environ
elements (%s=%s)
 (W internal) Warnings peculiar to
VMS. You tried to change or delete an
element of the CRTL's internal environ
array, but your copy of Perl wasn't built with a CRTL that contained the setenv() function.
You'll need to rebuild Perl with a CRTL that
does, or redefine PERL_ENV_TABLES
(see perlvms) so that the environ array isn't the target of the
change to %ENV which produced the warning.
Too late to run %s block
 (W void) A CHECK or
INIT block is being defined during run time
proper, when the opportunity to run them has already passed.
Perhaps you are loading a file with "require" or
"do" when you should be using "use" instead. Or
perhaps you should put the "require" or "do"
inside a BEGIN block.
Unknown open() mode '%s'
 (F) The second argument of 3-argument
open() is not among the list of valid modes:
"<", ">", ">>",
"+<", "+>", "+>>",
"-|", "|-".
Unknown process %x sent message to prime_env_iter: %s
 (P) An error peculiar to
VMS. Perl was reading values
for %ENV before iterating over it, and someone else stuck a
message in the stream of data Perl expected. Someone's very
confused, or perhaps trying to subvert Perl's population of
%ENV for nefarious purposes.
Unrecognized escape \\%c passed through
 (W misc) You used a backslash-character
combination which is not recognized by Perl. The character was
understood literally.
Unterminated attribute parameter in attribute list
 (F) The lexer saw an opening (left)
parenthesis character while parsing an attribute list, but the
matching closing (right) parenthesis character was not found. You
may need to add (or remove) a backslash character to get your
parentheses to balance. See attributes.
Unterminated attribute list
 (F) The lexer found something other than a
simple identifier at the start of an attribute, and it wasn't a
semicolon or the start of a block. Perhaps you terminated the
parameter list of the previous attribute too soon. See attributes.
Unterminated attribute parameter in subroutine attribute list
 (F) The lexer saw an opening (left)
parenthesis character while parsing a subroutine attribute list,
but the matching closing (right) parenthesis character was not
found. You may need to add (or remove) a backslash character to get
your parentheses to balance.
Unterminated subroutine attribute list
 (F) The lexer found something other than a
simple identifier at the start of a subroutine attribute, and it
wasn't a semicolon or the start of a block. Perhaps you terminated
the parameter list of the previous attribute too soon.
Value of CLI symbol %s too long
 (W misc) A warning peculiar to VMS. Perl tried to read the value of an %ENV
element from a CLI symbol table, and found a
resultant string longer than 1024 characters. The return value has
been truncated to 1024 characters.
Version number must be a constant number
 (P) The attempt to translate a "use
Module n.n LIST" statement into its equivalent
"BEGIN" block found an internal inconsistency with the
version number.

lib/attrs

Compatibility tests for "sub : attrs" vs the older "use attrs".

lib/env

Tests for new environment scalar capability (e.g., "use Env qw($BAR);").

lib/env-array

Tests for new environment array capability (e.g., "use Env qw(@PATH);").

lib/io_const

IO constants (SEEK_*, _IO*).

lib/io_dir

Directory-related IO methods (new, read, close, rewind, tied delete).

lib/io_multihomed

INET sockets with multi-homed hosts.

lib/io_poll

IO poll().

lib/io_unix

UNIX sockets.

op/attrs

Regression tests for "my ($x,@y,%z) : attrs" and <sub : attrs>.

op/filetest

File test operators.

op/lex_assign

Verify operations that access pad objects (lexicals and temporaries).

op/exists_sub

Verify "exists &sub" operations.

Since all new warnings must be explicitly requested via the "-w" switch or the "warnings" pragma, it is ultimately the programmer's responsibility to ensure that warnings are enabled judiciously.

CHECK is a new keyword

All subroutine definitions named CHECK are now special. See "/"Support for CHECK blocks"" for more information.

Treatment of list slices of undef has changed

There is a potential incompatibility in the behavior of list slices that are comprised entirely of undefined values. See ``Behavior of list slices is more consistent''.

Format of $English::PERL_VERSION is different

The English module now sets $PERL_VERSION to $^V (a string value) rather than $] (a numeric value). This is a potential incompatibility. Send us a report via perlbug if you are affected by this.

See ``Improved Perl version numbering system'' for the reasons for this change.

Literals of the form 1.2.3 parse differently

Previously, numeric literals with more than one dot in them were interpreted as a floating point number concatenated with one or more numbers. Such ``numbers'' are now parsed as strings composed of the specified ordinals.

For example, "print 97.98.99" used to output 97.9899 in earlier versions, but now prints "abc".

See ``Support for strings represented as a vector of ordinals''.

Possibly changed pseudo-random number generator

Perl programs that depend on reproducing a specific set of pseudo-random numbers may now produce different output due to improvements made to the rand() builtin. You can use "sh Configure -Drandfunc=rand" to obtain the old behavior.

See ``Better pseudo-random number generator''.

Hashing function for hash keys has changed

Even though Perl hashes are not order preserving, the apparently random order encountered when iterating on the contents of a hash is actually determined by the hashing algorithm used. Improvements in the algorithm may yield a random order that is different from that of previous versions, especially when iterating on hashes.

See ``Better worst-case behavior of hashes'' for additional information.

undef fails on read only values

Using the "undef" operator on a readonly value (such as $1) has the same effect as assigning "undef" to the readonly value---it throws an exception.

Close-on-exec bit may be set on pipe and socket handles

Pipe and socket handles are also now subject to the close-on-exec behavior determined by the special variable $^F.

See ``More consistent close-on-exec behavior''.

Writing $$1 to mean ${$}1 is unsupported

Perl 5.004 deprecated the interpretation of $$1 and similar within interpolated strings to mean "$$ . "1"", but still allowed it.

In Perl 5.6.0 and later, "$$1" always means "${$1}".

delete(), each(), values() and \(%h)

operate on aliases to values, not copies

delete(), each(), values() and hashes (e.g. "\(%h)") in a list context return the actual values in the hash, instead of copies (as they used to in earlier versions). Typical idioms for using these constructs copy the returned values, but this can make a significant difference when creating references to the returned values. Keys in the hash are still returned as copies when iterating on a hash.

See also ``delete(), each(), values() and hash iteration are faster''.

vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS

vec() generates a run-time error if the BITS argument is not a valid power-of-two integer.

Text of some diagnostic output has changed

Most references to internal Perl operations in diagnostics have been changed to be more descriptive. This may be an issue for programs that may incorrectly rely on the exact text of diagnostics for proper functioning.

%@ has been removed

The undocumented special variable "%@" that used to accumulate ``background'' errors (such as those that happen in DESTROY()) has been removed, because it could potentially result in memory leaks.

Parenthesized not() behaves like a list operator

The "not" operator now falls under the ``if it looks like a function, it behaves like a function'' rule.

As a result, the parenthesized form can be used with "grep" and "map". The following construct used to be a syntax error before, but it works as expected now:

    grep not($_), @things;

On the other hand, using "not" with a literal list slice may not work. The following previously allowed construct:

    print not (1,2,3)[0];

needs to be written with additional parentheses now:

    print not((1,2,3)[0]);

The behavior remains unaffected when "not" is not followed by parentheses.

Semantics of bareword prototype (*) have changed

The semantics of the bareword prototype "*" have changed. Perl 5.005 always coerced simple scalar arguments to a typeglob, which wasn't useful in situations where the subroutine must distinguish between a simple scalar and a typeglob. The new behavior is to not coerce bareword arguments to a typeglob. The value will always be visible as either a simple scalar or as a reference to a typeglob.

See ``More functional bareword prototype (*)''.

Semantics of bit operators may have changed on 64-bit platforms

If your platform is either natively 64-bit or if Perl has been configured to used 64-bit integers, i.e., $Config{ivsize} is 8, there may be a potential incompatibility in the behavior of bitwise numeric operators (& | ^ ~ << >>). These operators used to strictly operate on the lower 32 bits of integers in previous versions, but now operate over the entire native integral width. In particular, note that unary "~" will produce different results on platforms that have different $Config{ivsize}. For portability, be sure to mask off the excess bits in the result of unary "~", e.g., "~$x & 0xffffffff".

See ``Bit operators support full native integer width''.

More builtins taint their results

As described in ``Improved security features'', there may be more sources of taint in a Perl program.

To avoid these new tainting behaviors, you can build Perl with the Configure option "-Accflags=-DINCOMPLETE_TAINTS". Beware that the ensuing perl binary may be insecure.

PERL_POLLUTE

Release 5.005 grandfathered old global symbol names by providing preprocessor macros for extension source compatibility. As of release 5.6.0, these preprocessor definitions are not available by default. You need to explicitly compile perl with "-DPERL_POLLUTE" to get these definitions. For extensions still using the old symbols, this option can be specified via MakeMaker:

    perl Makefile.PL POLLUTE=1

PERL_IMPLICIT_CONTEXT

This new build option provides a set of macros for all API functions such that an implicit interpreter/thread context argument is passed to every API function. As a result of this, something like "sv_setsv(foo,bar)" amounts to a macro invocation that actually translates to something like "Perl_sv_setsv(my_perl,foo,bar)". While this is generally expected to not have any significant source compatibility issues, the difference between a macro and a real function call will need to be considered.

This means that there is a source compatibility issue as a result of this if your extensions attempt to use pointers to any of the Perl API functions.

Note that the above issue is not relevant to the default build of Perl, whose interfaces continue to match those of prior versions (but subject to the other options described here).

See ``The Perl API'' in perlguts for detailed information on the ramifications of building Perl with this option.

    NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
    with one of -Dusethreads, -Dusemultiplicity, or both.  It is not
    intended to be enabled by users at this time.

PERL_POLLUTE_MALLOC

Enabling Perl's malloc in release 5.005 and earlier caused the namespace of the system's malloc family of functions to be usurped by the Perl versions, since by default they used the same names. Besides causing problems on platforms that do not allow these functions to be cleanly replaced, this also meant that the system versions could not be called in programs that used Perl's malloc. Previous versions of Perl have allowed this behaviour to be suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor definitions.

As of release 5.6.0, Perl's malloc family of functions have default names distinct from the system versions. You need to explicitly compile perl with "-DPERL_POLLUTE_MALLOC" to get the older behaviour. HIDEMYMALLOC and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now the default.

Note that these functions do not constitute Perl's memory allocation API. See ``Memory Allocation'' in perlguts for further information about that.

Compatible C Source API Changes

PATCHLEVEL is now PERL_VERSION

The cpp macros "PERL_REVISION", "PERL_VERSION", and "PERL_SUBVERSION" are now available by default from perl.h, and reflect the base revision, patchlevel, and subversion respectively. "PERL_REVISION" had no prior equivalent, while "PERL_VERSION" and "PERL_SUBVERSION" were previously available as "PATCHLEVEL" and "SUBVERSION".

The new names cause less pollution of the cpp namespace and reflect what the numbers have come to stand for in common practice. For compatibility, the old names are still supported when patchlevel.h is explicitly included (as required before), so there is no source incompatibility from the change.

The usethreads or usemultiplicity builds are not binary compatible with the corresponding builds in 5.005.

On platforms that require an explicit list of exports (AIX, OS/2 and Windows, among others), purely internal symbols such as parser functions and the run time opcodes are not exported by default. Perl 5.005 used to export all functions irrespective of whether they were considered part of the public API or not.

For the full list of public API functions, see perlapi.

EBCDIC platforms not supported

NEXTSTEP 3.3 POSIX test failure

        Guessing which symbols your C compiler and preprocessor define...
        CC-20 cc: ERROR File = try.c, Line = 3
        ...
          bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
        ...
        4 errors detected in the compilation of "try.c".