perl588delta man page

perl588delta — what is new for perl v5.8.8


This document describes differences between the 5.8.7 release and the 5.8.8 release.

Incompatible Changes

There are no changes intentionally incompatible with 5.8.7. If any exist, they are bugs and reports are welcome.

Core Enhancements

Modules and Pragmata

Utility Changes

“h2xs” enhancements

"h2xs" implements new option "--use-xsloader" to force use of "XSLoader" even in backwards compatible modules.

The handling of authors' names that had apostrophes has been fixed.

Any enums with negative values are now skipped.

“perlivp” enhancements

"perlivp" implements new option "-a" and will not check for *.ph files by default any more.  Use the "-a" option to run all tests.

New Documentation

The perlglossary manpage is a glossary of terms used in the Perl documentation, technical and otherwise, kindly provided by O'Reilly Media, inc.

Performance Enhancements

Installation and Configuration Improvements

Parallel makes should work properly now, although there may still be problems if "make test" is instructed to run in parallel.

Building with Borland's compilers on Win32 should work more smoothly. In particular Steve Hay has worked to side step many warnings emitted by their compilers and at least one C compiler internal error.

"Configure" will now detect "clearenv" and "unsetenv", thanks to a patch from Alan Burlison. It will also probe for "futimes" and whether "sprintf" correctly returns the length of the formatted string, which will both be used in perl 5.8.9.

There are improved hints for next-3.0, vmesa, IX, Darwin, Solaris, Linux, DEC/OSF, HP-UX and MPE/iX

Perl extensions on Windows now can be statically built into the Perl DLL, thanks to a work by Vadim Konovalov. (This improvement was actually in 5.8.7, but was accidentally omitted from perl587delta).

Selected Bug Fixes

no warnings 'category' works correctly with -w

Previously when running with warnings enabled globally via "-w", selective disabling of specific warning categories would actually turn off all warnings. This is now fixed; now "no warnings 'io';" will only turn off warnings in the "io" class. Previously it would erroneously turn off all warnings.

This bug fix may cause some programs to start correctly issuing warnings.

Remove over-optimisation

Perl 5.8.4 introduced a change so that assignments of "undef" to a scalar, or of an empty list to an array or a hash, were optimised away. As this could cause problems when "goto" jumps were involved, this change has been backed out.

sprintf() fixes

Using the sprintf() function with some formats could lead to a buffer overflow in some specific cases. This has been fixed, along with several other bugs, notably in bounds checking.

In related fixes, it was possible for badly written code that did not follow the documentation of "Sys::Syslog" to have formatting vulnerabilities. "Sys::Syslog" has been changed to protect people from poor quality third party code.

Debugger and Unicode slowdown

It had been reported that running under perl's debugger when processing Unicode data could cause unexpectedly large slowdowns. The most likely cause of this was identified and fixed by Nicholas Clark.

Smaller fixes

  • "FindBin" now works better with directories where access rights are more restrictive than usual.
  • Several memory leaks in ithreads were closed. An improved implementation of "threads::shared" is available on CPAN - this will be merged into 5.8.9 if it proves stable.
  • Trailing spaces are now trimmed from $! and $^E.
  • Operations that require perl to read a process's list of groups, such as reads of $( and $), now dynamically allocate memory rather than using a fixed sized array. The fixed size array could cause C stack exhaustion on systems configured to use large numbers of groups.
  • "PerlIO::scalar" now works better with non-default $/ settings.
  • You can now use the "x" operator to repeat a "qw//" list. This used to raise a syntax error.
  • The debugger now traces correctly execution in eval("")uated code that contains #line directives.
  • The value of the "open" pragma is no longer ignored for three-argument opens.
  • The optimisation of "for (reverse @a)" introduced in perl 5.8.6 could misbehave when the array had undefined elements and was used in LVALUE context. Dave Mitchell provided a fix.
  • Some case insensitive matches between UTF-8 encoded data and 8 bit regexps, and vice versa, could give malformed character warnings. These have been fixed by Dave Mitchell and Yves Orton.
  • "lcfirst" and "ucfirst" could corrupt the string for certain cases where the length UTF-8 encoding of the string in lower case, upper case or title case differed. This was fixed by Nicholas Clark.
  • Perl will now use the C library calls "unsetenv" and "clearenv" if present to delete keys from %ENV and delete %ENV entirely, thanks to a patch from Alan Burlison.

New or Changed Diagnostics

Attempt to set length of freed array

This is a new warning, produced in situations such as this:

    $r = do {my @a; \$#a};
    $$r = 503;

Non-string passed as bitmask

This is a new warning, produced when number has been passed as a argument to select(), instead of a bitmask.

    # Wrong, will now warn
    $rin = fileno(STDIN);
    ($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout);
    # Should be
    $rin = '';
    vec($rin,fileno(STDIN),1) = 1;
    ($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout);

Search pattern not terminated or ternary operator parsed as search pattern

This syntax error indicates that the lexer couldn't find the final delimiter of a "?PATTERN?" construct. Mentioning the ternary operator in this error message makes it easier to diagnose syntax errors.

Changed Internals

There has been a fair amount of refactoring of the "C" source code, partly to make it tidier and more maintainable. The resulting object code and the "perl" binary may well be smaller than 5.8.7, in particular due to a change contributed by Dave Mitchell which reworked the warnings code to be significantly smaller. Apart from being smaller and possibly faster, there should be no user-detectable changes.

Andy Lester supplied many improvements to determine which function parameters and local variables could actually be declared "const" to the C compiler. Steve Peters provided new *_set macros and reworked the core to use these rather than assigning to macros in LVALUE context.

Dave Mitchell improved the lexer debugging output under "-DT"

Nicholas Clark changed the string buffer allocation so that it is now rounded up to the next multiple of 4 (or 8 on platforms with 64 bit pointers). This should reduce the number of calls to "realloc" without actually using any extra memory.

The "HV"'s array of "HE*"s is now allocated at the correct (minimal) size, thanks to another change by Nicholas Clark. Compile with "-DPERL_USE_LARGE_HV_ALLOC" to use the old, sloppier, default.

For XS or embedding debugging purposes, if perl is compiled with "-DDEBUG_LEAKING_SCALARS_FORK_DUMP" in addition to "-DDEBUG_LEAKING_SCALARS" then a child process is "fork"ed just before global destruction, which is used to display the values of any scalars found to have leaked at the end of global destruction. Without this, the scalars have already been freed sufficiently at the point of detection that it is impossible to produce any meaningful dump of their contents.  This feature was implemented by the indefatigable Nicholas Clark, based on an idea by Mike Giroux.

Platform Specific Problems

The optimiser on HP-UX 11.23 (Itanium 2) is currently partly disabled (scaled down to +O1) when using HP C-ANSI-C; the cause of problems at higher optimisation levels is still unclear.

There are a handful of remaining test failures on VMS, mostly due to test fixes and minor module tweaks with too many dependencies to integrate into this release from the development stream, where they have all been corrected.  The following is a list of expected failures with the patch number of the fix where that is known:

    ext/Devel/PPPort/t/ppphtest.t  #26913
    ext/List/Util/t/p_tainted.t    #26912
    lib/ExtUtils/t/PL_FILES.t      #26813
    lib/ExtUtils/t/basic.t         #26813

Reporting Bugs

If you find what you think is a bug, you might check the articles recently posted to the comp.lang.perl.misc newsgroup and the perl bug database at  There may also be information at, the Perl Home Page.

If you believe you have an unreported bug, please run the perlbug program included with your release.  Be sure to trim your bug down to a tiny but sufficient test case.  Your bug report, along with the output of "perl -V", will be sent off to to be analysed by the Perl porting team.  You can browse and search the Perl 5 bugs at

See Also

The Changes file for exhaustive details on what changed.

The INSTALL file for how to build Perl.

The README file for general stuff.

The Artistic and Copying files for copyright information.


2016-07-14 perl v5.24.1 Perl Programmers Reference Guide