3 release_managers_guide - Releasing a new version of perl 5.x
5 As of August 2009, this file is mostly complete, although it is missing
6 some detail on doing a major release (e.g. 5.10.0 -> 5.12.0). Note that
7 things change at each release, so there may be new things not covered
8 here, or tools may need updating.
12 This document describes the series of tasks required - some automatic, some
13 manual - to produce a perl release of some description, be that a snaphot,
14 release candidate, or final, numbered release of maint or blead.
16 The release process has traditionally been executed by the current
17 pumpking. Blead releases from 5.11.0 forward are made each month on the
18 20th by a non-pumpking release engineer. The release engineer roster
19 and schedule can be found in Porting/release_schedule.pod.
21 This document both helps as a check-list for the release engineer
22 and is a base for ideas on how the various tasks could be automated
25 The outline of a typical release cycle is as follows:
27 (5.10.1 is released, and post-release actions have been done)
31 an occasional snapshot is released, that still identifies itself as
36 a few weeks before the release, a number of steps are performed,
37 including bumping the version to 5.10.2
39 ...a few weeks passes...
41 perl-5.10.2-RC1 is released
43 perl-5.10.2 is released
45 post-release actions are performed, including creating new
48 ... the cycle continues ...
52 Some of the tasks described below apply to all four types of
53 release of Perl. (snapshot, RC, final release of maint, final
54 release of blead). Some of these tasks apply only to a subset
55 of these release types. If a step does not apply to a given
56 type of release, you will see a notation to that effect at
57 the beginning of the step.
65 A snapshot is intended to encourage in-depth testing from time-to-time,
66 for example after a key point in the stabilisation of a branch. It
67 requires fewer steps than a full release, and the version number of perl in
68 the tarball will usually be the same as that of the previous release.
70 =item Release Candidate (RC)
72 A release candidate is an attempt to produce a tarball that is a close as
73 possible to the final release. Indeed, unless critical faults are found
74 during the RC testing, the final release will be identical to the RC
75 barring a few minor fixups (updating the release date in F<perlhist.pod>,
76 removing the RC status from F<patchlevel.h>, etc). If faults are found,
77 then the fixes should be put into a new release candidate, never directly
80 =item Stable/Maint release
82 At this point you should have a working release candidate with few or no
85 It's essentially the same procedure as for making a release candidate, but
86 with a whole bunch of extra post-release steps.
90 It's essentially the same procedure as for making a release candidate, but
91 with a whole bunch of extra post-release steps.
97 Before you can make an official release of perl, there are a few
98 hoops you need to jump through:
104 I<SKIP this step for SNAPSHOT>
106 Make sure you have a PAUSE account suitable for uploading a perl release.
107 If you don't have a PAUSE account, then request one:
109 https://pause.perl.org/pause/query?ACTION=request_id
111 Check that your account is allowed to upload perl distros: goto
112 L<https://pause.perl.org/>, login, then select 'upload file to CPAN'; there
113 should be a "For pumpkings only: Send a CC" tickbox. If not, ask Andreas
114 König to add your ID to the list of people allowed to upload something
115 called perl. You can find Andreas' email address at:
117 https://pause.perl.org/pause/query?ACTION=pause_04imprint
119 =item search.cpan.org
121 Make sure that search.cpan.org knows that you're allowed to upload
122 perl distros. Contact Graham Barr to make sure that you're on the right
127 Some release engineering steps require a full mirror of the CPAN.
128 Work to fall back to using a remote mirror via HTTP is incomplete
129 but ongoing. (No, a minicpan mirror is not sufficient)
131 =item git checkout and commit bit
133 You will need a working C<git> installation, checkout of the perl
134 git repository and perl commit bit. For information about working
135 with perl and git, see F<pod/perlrepository.pod>.
137 If you are not yet a perl committer, you won't be able to make a
138 release. Have a chat with whichever evil perl porter tried to talk
139 you into the idea in the first place to figure out the best way to
143 =item Quotation for release announcement epigraph
145 I<SKIP this step for SNAPSHOT and RC>
147 For a numbered blead or maint release of perl, you will need a quotation
148 to use as an epigraph to your release announcement. (There's no harm
149 in having one for a snapshot, but it's not required).
154 =head2 Building a release - advance actions
156 The work of building a release candidate for a numbered release of
157 perl generally starts several weeks before the first release candidate.
158 Some of the following steps should be done regularly, but all I<must> be
159 done in the run up to a release.
165 I<You MAY SKIP this step for SNAPSHOT>
167 Ensure that dual-life CPAN modules are synchronised with CPAN. Basically,
170 $ ./perl -Ilib Porting/core-cpan-diff -a -o /tmp/corediffs
172 to see any inconsistencies between the core and CPAN versions of distros,
173 then fix the core, or cajole CPAN authors as appropriate. See also the
174 C<-d> and C<-v> options for more detail. You'll probably want to use the
175 C<-c cachedir> option to avoid repeated CPAN downloads.
177 To see which core distro versions differ from the current CPAN versions:
179 $ ./perl -Ilib Porting/core-cpan-diff -x -a
181 If you are making a maint release, run C<core-cpan-diff> on both blead and
182 maint, then diff the two outputs. Compare this with what you expect, and if
183 necessary, fix things up. For example, you might think that both blead
184 and maint are synchronised with a particular CPAN module, but one might
185 have some extra changes.
189 I<You MAY SKIP this step for SNAPSHOT>
191 Ensure dual-life CPAN modules are stable, which comes down to:
193 for each module that fails its regression tests on $current
194 did it fail identically on $previous?
195 if yes, "SEP" (Somebody Else's Problem)
196 else work out why it failed (a bisect is useful for this)
198 attempt to group failure causes
200 for each failure cause
201 is that a regression?
202 if yes, figure out how to fix it
203 (more code? revert the code that broke it)
205 (presumably) it's relying on something un-or-under-documented
206 should the existing behaviour stay?
207 yes - goto "regression"
208 no - note it in perldelta as a significant bugfix
209 (also, try to inform the module's author)
213 I<You MAY SKIP this step for SNAPSHOT>
215 Similarly, monitor the smoking of core tests, and try to fix.
219 I<You MAY SKIP this step for SNAPSHOT>
221 Similarly, monitor the smoking of perl for compiler warnings, and try to
226 I<You MAY SKIP this step for SNAPSHOT>
228 Run F<Porting/cmpVERSION.pl> to compare the current source tree with the
229 previous version to check for for modules that have identical version
230 numbers but different contents, e.g.:
232 $ cd ~/some-perl-root
233 $ ./perl -Ilib Porting/cmpVERSION.pl -xd ~/my_perl-tarballs/perl-5.10.0 .
235 then bump the version numbers of any non-dual-life modules that have
236 changed since the previous release, but which still have the old version
237 number. If there is more than one maintenance branch (e.g. 5.8.x, 5.10.x),
238 then compare against both.
240 Note that some of the files listed may be generated (e.g. copied from ext/
241 to lib/, or a script like lib/lib_pm.PL is run to produce lib/lib.pm);
242 make sure you edit the correct file!
244 Once all version numbers have been bumped, re-run the checks.
246 Then run again without the -x option, to check that dual-life modules are
249 $ ./perl -Ilib Porting/cmpVERSION.pl -d ~/my_perl-tarballs/perl-5.10.0 .
253 I<You MAY SKIP this step for SNAPSHOT>
255 Get perldelta in a mostly finished state.
257 Peruse F<Porting/how_to_write_a_perldelta.pod>, and try to make sure that
258 every section it lists is, if necessary, populated and complete. Copy
259 edit the whole document.
263 I<You MUST SKIP this step for SNAPSHOT>
265 A week or two before the first release candidate, bump the perl version
266 number (e.g. from 5.10.0 to 5.10.1), to allow sufficient time for testing
267 and smoking with the target version built into the perl executable. For
268 subsequent release candidates and the final release, it it not necessary
269 to bump the version further.
271 There is a tool to semi-automate this process. It works in two stages.
272 First, it generates a list of suggested changes, which you review and
273 edit; then you feed this list back and it applies the edits. So, first
274 scan the source directory looking for likely candidates. The command line
275 arguments are the old and new version numbers, and -s means scan:
277 $ Porting/bump-perl-version -s 5.10.0 5.10.1 > /tmp/scan
279 This produces a file containing a list of suggested edits, e.g.:
283 89: -MODULE_DESC = "Perl 5.10.0 for NetWare"
284 +MODULE_DESC = "Perl 5.10.1 for NetWare"
286 i.e. in the file F<NetWare/Makefile>, line 89 would be changed as shown.
287 Review the file carefully, and delete any -/+ line pairs that you don't
288 want changing. You can also edit just the C<+> line to change the
289 suggested replacement text. Remember that this tool is largely just
290 grepping for '5.10.0' or whatever, so it will generate false positives. Be
291 careful not change text like "this was fixed in 5.10.0"! Then run:
293 $ Porting/bump-perl-version -u < /tmp/scan
295 which will update all the files shown.
297 Be particularly careful with F<INSTALL>, which contains a mixture of
298 C<5.10.0>-type strings, some of which need bumping on every release, and
299 some of which need to be left unchanged. Also note that this tool
300 currently only detects a single substitution per line: so in particular,
301 this line in README.vms needs special handling:
303 rename perl-5^.10^.1.dir perl-5_10_1.dir
305 Have a look a couple lines up from that. You'll see roman numerals.
306 Update those too. Find someone with VMS clue if you have to update
307 the Roman numerals for a .0 release.
313 B<review the delta carefully>
315 $ git commit -a -m 'Bump the perl version in various places for 5.x.y'
317 When the version number is bumped, you should also update Module::CoreList (as
318 described below in L<"Building a release - on the day">) to reflect the new
323 I<You MUST SKIP this step for SNAPSHOT>
325 Review and update INSTALL to account for the change in version number;
326 in particular, the "Coexistence with earlier versions of perl 5" section.
330 Check some more build configurations. The check that setuid builds and
331 installs is for < 5.11.0 only.
333 $ sh Configure -Dprefix=/tmp/perl-5.x.y -Uinstallusrbinperl \
334 -Duseshrplib -Dd_dosuid
336 $ LD_LIBRARY_PATH=`pwd` make test # or similar for useshrplib
339 $ su -c 'make install'
340 $ ls -l .../bin/sperl
341 -rws--x--x 1 root root 69974 2009-08-22 21:55 .../bin/sperl
343 (Then delete the installation directory.)
345 XXX think of other configurations that need testing.
349 I<You MAY SKIP this step for SNAPSHOT>
351 Update F<AUTHORS>, using the C<Porting/checkAUTHORS.pl> script, and if
352 necessary, update the script to include new alias mappings for porters
353 already in F<AUTHORS>
355 $ git log | perl Porting/checkAUTHORS.pl --acknowledged AUTHORS -
359 =head2 Building a release - on the day
361 This section describes the actions required to make a release (or snapshot
362 etc) that are performed on the actual day.
368 Review all the items in the previous section,
369 L<"Building a release - advance actions"> to ensure they are all done and
374 I<You MAY SKIP this step for SNAPSHOT>
376 Re-read the perldelta to try to find any embarrassing typos and thinkos;
377 remove any C<TODO> or C<XXX> flags; update the "Known Problems" section
378 with any serious issues for which fixes are not going to happen now; and
379 run through pod and spell checkers, e.g.
381 $ podchecker -warnings -warnings pod/perl5101delta.pod
382 $ spell pod/perl5101delta.pod
384 Also, you may want to generate and view an HTML version of it to check
387 $ perl pod/pod2html pod/perl5101delta.pod > /tmp/perl5101delta.html
391 Make sure you have a gitwise-clean perl directory (no modified files,
392 unpushed commits etc):
398 If not already built, Configure and build perl so that you have a Makefile
401 $ ./Configure -Dusedevel -des && make
405 Check that files managed by F<regen.pl> and friends are up to date. From
406 within your working directory:
413 If any of the files managed by F<regen.pl> have changed, then you should
414 re-make perl to check that it's okay, then commit the updated versions:
416 $ git commit -a -m 'make regen; make regen_perly'
426 XXX it would be nice to make Porting/makemeta use regen_lib.pl
427 to get the same 'update the file if its changed' functionality
428 we get with 'make regen' etc.
430 Commit META.yml if it has changed:
432 $ git commit -m 'Update META.yml' META.yml
436 I<You MUST SKIP this step for SNAPSHOT>
438 Update C<Module::Corelist> with module version data for the new release.
440 Note that if this is a maint release, you should run the following actions
441 from the maint directory, but commit the C<Corelist.pm> changes in
442 I<blead> and subsequently cherry-pick it.
444 F<corelist.pl> uses ftp.funet.fi to verify information about dual-lived
445 modules on CPAN. It can use a full, local CPAN mirror or fall back
446 to C<wget> or C<curl> to fetch only package metadata remotely.
448 (If you'd prefer to have a full CPAN mirror, see
449 http://www.cpan.org/misc/cpan-faq.html#How_mirror_CPAN)
451 Then change to your perl checkout, and if necessary,
455 If this not the first update for this version (e.g. if it was updated
456 when the version number was originally bumped), first edit
457 F<dist/Module-CoreList/lib/Module/CoreList.pm> to delete the existing
458 entries for this version from the C<%released> and C<%version> hashes:
459 they will have a key like C<5.010001> for 5.10.1.
461 XXX the edit-in-place functionality of Porting/corelist.pl should
462 be fixed to handle this automatically.
464 Then, If you have a local CPAN mirror, run:
466 $ ./perl -Ilib Porting/corelist.pl ~/my-cpan-mirror
470 $ ./perl -Ilib Porting/corelist.pl cpan
472 This will chug for a while, possibly reporting various warnings about
473 badly-indexed CPAN modules unrelated to the modules actually in core.
474 Assuming all goes well, it will update
475 F<dist/Module-CoreList/lib/Module/CoreList.pm>.
477 Check that file over carefully:
479 $ git diff dist/Module-CoreList/lib/Module/CoreList.pm
481 If necessary, bump C<$VERSION> (there's no need to do this for
482 every RC; in RC1, bump the version to a new clean number that will
483 appear in the final release, and leave as-is for the later RCs and final).
485 Edit the version number in the new C<< 'Module::CoreList' => 'X.YZ' >>
486 entry, as that is likely to reflect the previous version number.
488 In addition, if this is a final release (rather than a release candidate):
494 Update this version's entry in the C<%released> hash with today's date.
498 Make sure that the script has correctly updated the C<CAVEATS> section
502 Finally, commit the new version of Module::CoreList:
503 (unless this is for maint; in which case commit it blead first, then
504 cherry-pick it back).
506 $ git commit -m 'Update Module::CoreList for 5.x.y' dist/Module-CoreList/lib/Module/CoreList.pm
510 Check that the manifest is sorted and correct:
514 $ git clean -xdf # This shouldn't be necessary if distclean is correct
515 $ perl Porting/manicheck
518 XXX manifest _sorting_ is now checked with make test_porting
520 Commit MANIFEST if it has changed:
522 $ git commit -m 'Update MANIFEST' MANIFEST
526 I<You MUST SKIP this step for SNAPSHOT>
528 Add an entry to F<pod/perlhist.pod> with the current date, e.g.:
530 David 5.10.1-RC1 2009-Aug-06
532 Make sure that the correct pumpking is listed in the left-hand column, and
533 if this is the first release under the stewardship of a new pumpking, make
534 sure that his or her name is listed in the section entitled
535 C<THE KEEPERS OF THE PUMPKIN>.
537 Be sure to commit your changes:
539 $ git commit -m 'add new release to perlhist' pod/perlhist.pod
543 I<You MUST SKIP this step for SNAPSHOT>
545 Update F<patchlevel.h> to add a C<-RC1>-or-whatever string; or, if this is
546 a final release, remove it. For example:
548 static const char * const local_patches[] = {
551 PERL_GIT_UNPUSHED_COMMITS /* do not remove this line */
553 Be sure to commit your change:
555 $ git commit -m 'bump version to RCnnn' patchlevel.h
559 Build perl, then make sure it passes its own test suite, and installs:
562 $ ./Configure -des -Dprefix=/tmp/perl-5.x.y-pretest
564 # or if it's an odd-numbered version:
565 $ ./Configure -des -Dusedevel -Dprefix=/tmp/perl-5.x.y-pretest
571 Check that the output of C</tmp/perl-5.x.y-pretest/bin/perl -v> and
572 C</tmp/perl-5.x.y-pretest/bin/perl -V> are as expected,
573 especially as regards version numbers, patch and/or RC levels, and @INC
574 paths. Note that as they have been been built from a git working
575 directory, they will still identify themselves using git tags and
578 Then delete the temporary installation.
582 If this is maint release, make sure F<Porting/mergelog> is saved and
587 Push all your recent commits:
589 $ git push origin ....
594 I<You MUST SKIP this step for SNAPSHOT>
598 $ git tag v5.11.0 -m'First release of the v5.11 series!'
600 It is VERY important that from this point forward, you not push
601 your git changes to the Perl master repository. If anything goes
602 wrong before you publish your newly-created tag, you can delete
603 and recreate it. Once you push your tag, we're stuck with it
604 and you'll need to use a new version number for your release.
608 Create a tarball. Use the C<-s> option to specify a suitable suffix for
609 the tarball and directory name:
611 $ cd root/of/perl/tree
613 $ git clean -xdf # make sure perl and git agree on files
614 $ git status # and there's nothing lying around
616 $ perl Porting/makerel -b -s `git describe` # for a snapshot
617 $ perl Porting/makerel -b -s RC1 # for a release candidate
618 $ perl Porting/makerel -b # for a final release
620 This creates the directory F<../perl-x.y.z-RC1> or similar, copies all
621 the MANIFEST files into it, sets the correct permissions on them,
622 adds DOS line endings to some, then tars it up as
623 F<../perl-x.y.z-RC1.tar.gz>. With C<-b>, it also creates a C<tar.bz2> file.
626 XXX if we go for extra tags and branches stuff, then add the extra details
631 Clean up the temporary directory, e.g.
633 $ rm -rf ../perl-x.y.z-RC1
637 Copy the tarballs (.gz and possibly .bz2) to a web server somewhere you
642 Download the tarball to some other machine. For a release candidate,
643 you really want to test your tarball on two or more different platforms
644 and architectures. The #p5p IRC channel on irc.perl.org is a good place
645 to find willing victims.
649 Check that basic configuration and tests work on each test machine:
651 $ ./Configure -des && make all test
655 Check that the test harness and install work on each test machine:
658 $ ./Configure -des -Dprefix=/install/path && make all test_harness install
663 Check that the output of C<perl -v> and C<perl -V> are as expected,
664 especially as regards version numbers, patch and/or RC levels, and @INC
667 Note that the results may be different without a F<.git/> directory,
668 which is why you should test from the tarball.
672 Run the Installation Verification Procedure utility:
676 All tests successful.
681 Compare the pathnames of all installed files with those of the previous
682 release (i.e. against the last installed tarball on this branch which you
683 have previously verified using this same procedure). In particular, look
684 for files in the wrong place, or files no longer included which should be.
685 For example, suppose the about-to-be-released version is 5.10.1 and the
688 cd installdir-5.10.0/
689 find . -type f | perl -pe's/5\.10\.0/5.10.1/g' | sort > /tmp/f1
690 cd installdir-5.10.1/
691 find . -type f | sort > /tmp/f2
696 Bootstrap the CPAN client on the clean install:
698 $ bin/perl -MCPAN -e'shell'
702 Try installing a popular CPAN module that's reasonably complex and that
703 has dependencies; for example:
708 Check that your perl can run this:
710 $ bin/perl -lwe 'use Inline C => "int f() { return 42;} "; print f'
716 Bootstrap the CPANPLUS client on the clean install:
722 Install an XS module, for example:
726 $ bin/perl -MDBI -e 1
731 I<If you're building a SNAPSHOT, you should STOP HERE>
735 Check that the C<perlbug> utility works. Try the following:
739 Subject: test bug report
740 Local perl administrator [yourself]:
746 Action (Send/Display/Edit/Subject/Save to File): f
747 Name of file to save message in [perlbug.rep]:
748 Action (Send/Display/Edit/Subject/Save to File): q
750 and carefully examine the output (in F<perlbug.rep]>), especially
751 the "Locally applied patches" section. If everything appears okay, then
752 delete the file, and try it again, this time actually submitting the bug
753 report. Check that it shows up, then remember to close it!
757 Wait for the smoke tests to catch up with the commit which this release is
758 based on (or at least the last commit of any consequence).
760 Then check that the smoke tests pass (particularly on Win32). If not, go
766 Once smoking is okay, upload it to PAUSE. This is the point of no return.
767 If anything goes wrong after this point, you will need to re-prepare
768 a new release with a new minor version or RC number.
770 https://pause.perl.org/
772 (Login, then select 'Upload a file to CPAN')
774 Upload both the .gz and .bz2 versions of the tarball.
778 Now that you've shipped the new perl release to PAUSE, it's
779 time to publish the tag you created earlier to the public git repo:
781 $ git push origin tag v5.11.0
785 Disarm the F<patchlevel.h> change; for example,
787 static const char * const local_patches[] = {
790 PERL_GIT_UNPUSHED_COMMITS /* do not remove this line */
792 Be sure to commit your change:
794 $ git commit -m 'disarm RCnnn bump' patchlevel.h
795 $ git push origin ....
800 Mail p5p to announce your new release, with a quote you prepared earlier.
804 Wait 24 hours or so, then post the announcement to use.perl.org.
805 (if you don't have access rights to post news, ask someone like Rafael to
810 Ask Jarkko to add the tarball to http://www.cpan.org/src/
814 I<You MUST SKIP this step for RC, BLEAD>
816 Ask Jarkko to update the descriptions of which tarballs are current in
817 http://www.cpan.org/src/README.html, and Rafael to update
818 http://dev.perl.org/perl5/
822 I<You MUST SKIP this step for RC>
824 Remind the current maintainer of C<Module::CoreList> to push a new release
829 I<You MUST SKIP this step for RC>
831 Bump the perlXYZ version number.
833 First, create a new empty perlNNNdelta.pod file for the current release + 1;
834 see F<Porting/how_to_write_a_perldelta.pod>.
836 You should be able to do this by just copying in a skeleton template and
837 then doing a quick fix up of the version numbers, e.g.
839 $ cp -i Porting/perldelta_template.pod pod/perl5102delta.pod
841 $ git add pod/perl5102delta.pod
843 Edit F<pod.lst>: add the new entry, flagged as 'D', and unflag the previous
844 entry from being 'D'; for example:
846 -D perl5101delta Perl changes in version 5.10.1
847 +D perl5102delta Perl changes in version 5.10.2
848 + perl5101delta Perl changes in version 5.10.1
850 Run C<perl pod/buildtoc --build-all> to update the F<perldelta> version in
857 vms/descrip_mms.template
862 Then manually edit (F<vms/descrip_mms.template> to bump the version
863 in the following entry:
865 [.pod]perldelta.pod : [.pod]perl5101delta.pod
867 XXX this previous step needs to fixed to automate it in pod/buildtoc.
869 Manually update references to the perlNNNdelta version in these files:
874 Edit the previous delta file to change the C<NAME> from C<perldelta>
877 These two lists of files probably aren't exhaustive; do a recursive grep
878 on the previous filename to look for suitable candidates that may have
883 $ git commit -a -m 'create perlXXXdelta'
885 At this point you may want to compare the commit with a previous bump to
886 see if they look similar. See commit ca8de22071 for an example of a
887 previous version bump.
891 I<You MUST SKIP this step for RC, BLEAD>
893 If this was a maint release, then edit F<Porting/mergelog> to change
894 all the C<d> (deferred) flags to C<.> (needs review).
898 I<You MUST SKIP this step for RC, BLEAD>
900 If this was a major release (5.x.0), then create a new maint branch
901 based on the commit tagged as the current release and bump the version
902 in the blead branch in git, e.g. 5.12.0 to 5.13.0.
904 [ XXX probably lots more stuff to do, including perldelta,
907 XXX need a git recipe
911 I<You MUST SKIP this step for RC, BLEAD>
913 Copy the perlNNNdelta.pod for this release into the other branches; for
916 $ cp -i ../5.10.x/pod/perl5101delta.pod pod/ # for example
917 $ git add pod/perl5101delta.pod
919 Edit F<pod.lst> to add an entry for the file, e.g.:
921 perl5101delta Perl changes in version 5.10.1
923 Then rebuild various files:
925 $ perl pod/buildtoc --build-all
929 $ git commit -a -m 'add perlXXXdelta'
933 Make sure any recent F<pod/perlhist.pod> entries are copied to
934 F<perlhist.pod> on other branches; typically the RC* and final entries,
937 5.8.9-RC1 2008-Nov-10
938 5.8.9-RC2 2008-Dec-06
943 I<You MUST RETIRE to your preferred PUB, CAFE or SEASIDE VILLA for some
944 much-needed rest and relaxation>.
946 Thanks for releasing perl!
953 http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2009-05/msg00608.html,
954 plus a whole bunch of other sources, including private correspondence.