X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperltodo.pod;h=7c7dc96e3ff286fa90f67225dd83019c7c5427f3;hb=e40b81a3dd247b1a29fc78399677b77b78b5f183;hp=219e92ba028b02fbe3dc124ba26e8c768e5ed071;hpb=fa11829f4b6d56533794dd127f3d1068d9593670;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/pod/perltodo.pod b/pod/perltodo.pod
index 219e92b..7c7dc96 100644
--- a/pod/perltodo.pod
+++ b/pod/perltodo.pod
@@ -4,84 +4,429 @@ perltodo - Perl TO-DO List
 
 =head1 DESCRIPTION
 
-This is a list of wishes for Perl.  Send updates to
-I<perl5-porters@perl.org>.  If you want to work on any of these
-projects, be sure to check the perl5-porters archives for past ideas,
-flames, and propaganda.  This will save you time and also prevent you
-from implementing something that Larry has already vetoed.  One set
-of archives may be found at:
+This is a list of wishes for Perl. The tasks we think are smaller or easier
+are listed first. Anyone is welcome to work on any of these, but it's a good
+idea to first contact I<perl5-porters@perl.org> to avoid duplication of
+effort. By all means contact a pumpking privately first if you prefer.
+
+Whilst patches to make the list shorter are most welcome, ideas to add to
+the list are also encouraged. Check the perl5-porters archives for past
+ideas, and any discussion about them. One set of archives may be found at:
 
     http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/
 
-=head1 assertions
+What can we offer you in return? Fame, fortune, and everlasting glory? Maybe
+not, but if your patch is incorporated, then we'll add your name to the
+F<AUTHORS> file, which ships in the official distribution. How many other
+programming languages offer you 1 line of immortality?
 
-Clean up and finish support for assertions. See L<assertions>.
+=head1 The roadmap to 5.10
 
-=head1 iCOW
+The roadmap to 5.10 envisages feature based releases, as various items in this
+TODO are completed.
 
-Sarathy and Arthur have a proposal for an improved Copy On Write which
-specifically will be able to COW new ithreads. If this can be implemented
-it would be a good thing.
+=head2 Needed for the final 5.10.0 release
 
-=head1 (?{...}) closures in regexps
+Review perlguts. Significant changes have occured since 5.8, and we can't
+release a new version without making sure these are covered.
 
-Fix (or rewrite) the implementation of the C</(?{...})/> closures.
+=head1 Tasks that only need Perl knowledge
 
-=head1 A re-entrant regexp engine
+=head2 common test code for timed bail out
 
-This will allow the use of a regex from inside (?{ }), (??{ }) and
-(?(?{ })|) constructs.
+Write portable self destruct code for tests to stop them burning CPU in
+infinite loops. This needs to avoid using alarm, as some of the tests are
+testing alarm/sleep or timers.
 
-=head1 pragmata
+=head2 POD -> HTML conversion in the core still sucks
 
-=head2 lexical pragmas
+Which is crazy given just how simple POD purports to be, and how simple HTML
+can be. It's not actually I<as> simple as it sounds, particularly with the
+flexibility POD allows for C<=item>, but it would be good to improve the
+visual appeal of the HTML generated, and to avoid it having any validation
+errors. See also L</make HTML install work>, as the layout of installation tree
+is needed to improve the cross-linking.
 
-Reimplement the mechanism of lexical pragmas to be more extensible. Fix
-current pragmas that don't work well (or at all) with lexical scopes or in
-run-time eval(STRING) (C<sort>, C<re>, C<encoding> for example). MJD has a
-preliminary patch that implements this.
+The addition of C<Pod::Simple> and its related modules may make this task
+easier to complete.
 
-=head2 use less 'memory'
+=head2 Parallel testing
 
-Investigate trade offs to switch out perl's choices on memory usage.
-Particularly perl should be able to give memory back.
+(This probably impacts much more than the core: also the Test::Harness
+and TAP::* modules on CPAN.)
+
+The core regression test suite is getting ever more comprehensive, which has
+the side effect that it takes longer to run. This isn't so good. Investigate
+whether it would be feasible to give the harness script the B<option> of
+running sets of tests in parallel. This would be useful for tests in
+F<t/op/*.t> and F<t/uni/*.t> and maybe some sets of tests in F<lib/>.
+
+Questions to answer
+
+=over 4
+
+=item 1
+
+How does screen layout work when you're running more than one test?
+
+=item 2
+
+How does the caller of test specify how many tests to run in parallel?
+
+=item 3
+
+How do setup/teardown tests identify themselves?
+
+=back
+
+Pugs already does parallel testing - can their approach be re-used?
+
+=head2 Make Schwern poorer
+
+We should have tests for everything. When all the core's modules are tested,
+Schwern has promised to donate to $500 to TPF. We may need volunteers to
+hold him upside down and shake vigorously in order to actually extract the
+cash.
+
+=head2 Improve the coverage of the core tests
+
+Use Devel::Cover to ascertain the core modules's test coverage, then add
+tests that are currently missing.
+
+=head2 test B
+
+A full test suite for the B module would be nice.
+
+=head2 A decent benchmark
+
+C<perlbench> seems impervious to any recent changes made to the perl core. It
+would be useful to have a reasonable general benchmarking suite that roughly
+represented what current perl programs do, and measurably reported whether
+tweaks to the core improve, degrade or don't really affect performance, to
+guide people attempting to optimise the guts of perl. Gisle would welcome
+new tests for perlbench.
+
+=head2 fix tainting bugs
+
+Fix the bugs revealed by running the test suite with the C<-t> switch (via
+C<make test.taintwarn>).
+
+=head2 Dual life everything
+
+As part of the "dists" plan, anything that doesn't belong in the smallest perl
+distribution needs to be dual lifed. Anything else can be too. Figure out what
+changes would be needed to package that module and its tests up for CPAN, and
+do so. Test it with older perl releases, and fix the problems you find.
+
+=head2 Improving C<threads::shared>
+
+Investigate whether C<threads::shared> could share aggregates properly with
+only Perl level changes to shared.pm
+
+=head2 POSIX memory footprint
+
+Ilya observed that use POSIX; eats memory like there's no tomorrow, and at
+various times worked to cut it down. There is probably still fat to cut out -
+for example POSIX passes Exporter some very memory hungry data structures.
+
+=head2 embed.pl/makedef.pl
+
+There is a script F<embed.pl> that generates several header files to prefix
+all of Perl's symbols in a consistent way, to provide some semblance of
+namespace support in C<C>. Functions are declared in F<embed.fnc>, variables
+in F<interpvar.h> and F<thrdvar.h>. Quite a few of the functions and variables
+are conditionally declared there, using C<#ifdef>. However, F<embed.pl>
+doesn't understand the C macros, so the rules about which symbols are present
+when is duplicated in F<makedef.pl>. Writing things twice is bad, m'kay.
+It would be good to teach C<embed.pl> to understand the conditional
+compilation, and hence remove the duplication, and the mistakes it has caused.
+
+=head2 use strict; and AutoLoad
+
+Currently if you write
+
+    package Whack;
+    use AutoLoader 'AUTOLOAD';
+    use strict;
+    1;
+    __END__
+    sub bloop {
+        print join (' ', No, strict, here), "!\n";
+    }
+
+then C<use strict;> isn't in force within the autoloaded subroutines. It would
+be more consistent (and less surprising) to arrange for all lexical pragmas
+in force at the __END__ block to be in force within each autoloaded subroutine.
+
+=head1 Tasks that need a little sysadmin-type knowledge
+
+Or if you prefer, tasks that you would learn from, and broaden your skills
+base...
+
+=head2 make HTML install work
+
+There is an C<installhtml> target in the Makefile. It's marked as
+"experimental". It would be good to get this tested, make it work reliably, and
+remove the "experimental" tag. This would include
+
+=over 4
+
+=item 1
+
+Checking that cross linking between various parts of the documentation works.
+In particular that links work between the modules (files with POD in F<lib/>)
+and the core documentation (files in F<pod/>)
+
+=item 2
+
+Work out how to split C<perlfunc> into chunks, preferably one per function
+group, preferably with general case code that could be used elsewhere.
+Challenges here are correctly identifying the groups of functions that go
+together, and making the right named external cross-links point to the right
+page. Things to be aware of are C<-X>, groups such as C<getpwnam> to
+C<endservent>, two or more C<=items> giving the different parameter lists, such
+as
+
+    =item substr EXPR,OFFSET,LENGTH,REPLACEMENT
+    =item substr EXPR,OFFSET,LENGTH
+    =item substr EXPR,OFFSET
+
+and different parameter lists having different meanings. (eg C<select>)
+
+=back
+
+=head2 compressed man pages
+
+Be able to install them. This would probably need a configure test to see how
+the system does compressed man pages (same directory/different directory?
+same filename/different filename), as well as tweaking the F<installman> script
+to compress as necessary.
+
+=head2 Add a code coverage target to the Makefile
+
+Make it easy for anyone to run Devel::Cover on the core's tests. The steps
+to do this manually are roughly
+
+=over 4
+
+=item *
+
+do a normal C<Configure>, but include Devel::Cover as a module to install
+(see F<INSTALL> for how to do this)
+
+=item *
+
+    make perl
+
+=item *
+
+    cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness
+
+=item *
+
+Process the resulting Devel::Cover database
+
+=back
+
+This just give you the coverage of the F<.pm>s. To also get the C level
+coverage you need to
+
+=over 4
+
+=item *
+
+Additionally tell C<Configure> to use the appropriate C compiler flags for
+C<gcov>
+
+=item *
+
+    make perl.gcov
+
+(instead of C<make perl>)
+
+=item *
+
+After running the tests run C<gcov> to generate all the F<.gcov> files.
+(Including down in the subdirectories of F<ext/>
+
+=item *
+
+(From the top level perl directory) run C<gcov2perl> on all the C<.gcov> files
+to get their stats into the cover_db directory.
+
+=item *
+
+Then process the Devel::Cover database
+
+=back
+
+It would be good to add a single switch to C<Configure> to specify that you
+wanted to perform perl level coverage, and another to specify C level
+coverage, and have C<Configure> and the F<Makefile> do all the right things
+automatically.
+
+=head2 Make Config.pm cope with differences between built and installed perl
+
+Quite often vendors ship a perl binary compiled with their (pay-for)
+compilers.  People install a free compiler, such as gcc. To work out how to
+build extensions, Perl interrogates C<%Config>, so in this situation
+C<%Config> describes compilers that aren't there, and extension building
+fails. This forces people into choosing between re-compiling perl themselves
+using the compiler they have, or only using modules that the vendor ships.
+
+It would be good to find a way teach C<Config.pm> about the installation setup,
+possibly involving probing at install time or later, so that the C<%Config> in
+a binary distribution better describes the installed machine, when the
+installed machine differs from the build machine in some significant way.
+
+=head2 linker specification files
+
+Some platforms mandate that you provide a list of a shared library's external
+symbols to the linker, so the core already has the infrastructure in place to
+do this for generating shared perl libraries. My understanding is that the
+GNU toolchain can accept an optional linker specification file, and restrict
+visibility just to symbols declared in that file. It would be good to extend
+F<makedef.pl> to support this format, and to provide a means within
+C<Configure> to enable it. This would allow Unix users to test that the
+export list is correct, and to build a perl that does not pollute the global
+namespace with private symbols.
+
+=head2 Cross-compile support
+
+Currently C<Configure> understands C<-Dusecrosscompile> option. This option
+arranges for building C<miniperl> for TARGET machine, so this C<miniperl> is
+assumed then to be copied to TARGET machine and used as a replacement of full
+C<perl> executable.
+
+This could be done little differently. Namely C<miniperl> should be built for
+HOST and then full C<perl> with extensions should be compiled for TARGET.
+This, however, might require extra trickery for %Config: we have one config
+first for HOST and then another for TARGET.
+
+=head1 Tasks that need a little C knowledge
+
+These tasks would need a little C knowledge, but don't need any specific
+background or experience with XS, or how the Perl interpreter works
+
+=head2 Make it clear from -v if this is the exact official release
+
+Currently perl from C<p4>/C<rsync> ships with a F<patchlevel.h> file that
+usually defines one local patch, of the form "MAINT12345" or "RC1". The output
+of perl -v doesn't report that a perl isn't an official release, and this
+information can get lost in bugs reports. Because of this, the minor version
+isn't bumped up until RC time, to minimise the possibility of versions of perl
+escaping that believe themselves to be newer than they actually are.
+
+It would be useful to find an elegant way to have the "this is an interim
+maintenance release" or "this is a release candidate" in the terse -v output,
+and have it so that it's easy for the pumpking to remove this just as the
+release tarball is rolled up. This way the version pulled out of rsync would
+always say "I'm a development release" and it would be safe to bump the
+reported minor version as soon as a release ships, which would aid perl
+developers.
+
+This task is really about thinking of an elegant way to arrange the C source
+such that it's trivial for the Pumpking to flag "this is an official release"
+when making a tarball, yet leave the default source saying "I'm not the
+official release".
+
+=head2 Ordering of "global" variables.
+
+F<thrdvar.h> and F<intrpvarh> define the "global" variables that need to be
+per-thread under ithreads, where the variables are actually elements in a
+structure. As C dictates, the variables must be laid out in order of
+declaration. There is a comment
+C</* Important ones in the first cache line (if alignment is done right) */>
+which implies that at some point in the past the ordering was carefully chosen
+(at least in part). However, it's clear that the ordering is less than perfect,
+as currently there are things such as 7 C<bool>s in a row, then something
+typically requiring 4 byte alignment, and then an odd C<bool> later on.
+(C<bool>s are typically defined as C<char>s). So it would be good for someone
+to review the ordering of the variables, to see how much alignment padding can
+be removed.
+
+It's also worth checking that all variables are actually used. Perl 5.8.0
+shipped with C<PL_nrs> still defined in F<thrdvar.h>, despite it being unused
+since a change over a year earlier. Had this been spotted before release, it
+could have been removed, but now it has to remain in the 5.8.x releases to
+keep the structure the same size, to retain binary compatibility.
+
+It's probably worth checking if all need to be the types they are. For example
+
+    PERLVAR(Ierror_count, I32)	/* how many errors so far, max 10 */
+
+might work as well if stored in a signed (or unsigned) 8 bit value, if the
+comment is accurate. C<PL_multi_open> and C<PL_multi_close> can probably
+become C<char>s. Finding variables to downsize coupled with rearrangement
+could shrink the interpreter structure; a size saving which is multiplied by
+the number of threads running.
+
+=head2 Profile Perl - am I hot or not?
+
+The Perl source code is stable enough that it makes sense to profile it,
+identify and optimise the hotspots. It would be good to measure the
+performance of the Perl interpreter using free tools such as cachegrind,
+gprof, and dtrace, and work to reduce the bottlenecks they reveal.
 
-=head1 prototypes and functions
+As part of this, the idea of F<pp_hot.c> is that it contains the I<hot> ops,
+the ops that are most commonly used. The idea is that by grouping them, their
+object code will be adjacent in the executable, so they have a greater chance
+of already being in the CPU cache (or swapped in) due to being near another op
+already in use.
 
-=head2 _ prototype character
+Except that it's not clear if these really are the most commonly used ops. So
+as part of exercising your skills with coverage and profiling tools you might
+want to determine what ops I<really> are the most commonly used. And in turn
+suggest evictions and promotions to achieve a better F<pp_hot.c>.
 
-Study the possibility of adding a new prototype character, C<_>, meaning
-"this argument defaults to $_".
+=head2 Allocate OPs from arenas
 
-=head2 inlining autoloaded constants
+Currently all new OP structures are individually malloc()ed and free()d.
+All C<malloc> implementations have space overheads, and are now as fast as
+custom allocates so it would both use less memory and less CPU to allocate
+the various OP structures from arenas. The SV arena code can probably be
+re-used for this.
 
-Currently the optimiser can inline constants when expressed as subroutines
-with prototype ($) that return a constant. Likewise, many packages wrapping
-C libraries export lots of constants as subroutines which are AUTOLOADed on
-demand. However, these have no prototypes, so can't be seen as constants by
-the optimiser. Some way of cheaply (low syntax, low memory overhead) to the
-perl compiler that a name is a constant would be great, so that it knows to
-call the AUTOLOAD routine at compile time, and then inline the constant.
+=head2 Improve win32/wince.c
 
-=head2 Finish off lvalue functions
+Currently, numerous functions look virtually, if not completely,
+identical in both C<win32/wince.c> and C<win32/win32.c> files, which can't
+be good.
 
-The old perltodo notes "They don't work in the debugger, and they don't work for
-list or hash slices."
+=head2 Use secure CRT functions when building with VC8 on Win32
 
-=head1 Unicode and UTF8
+Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis
+that they were "unsafe" and introduced differently named secure versions of
+them as replacements, e.g. instead of writing
 
-=head2 Implicit Latin 1 => Unicode translation
+    FILE* f = fopen(__FILE__, "r");
 
-Conversions from byte strings to UTF-8 currently map high bit characters
-to Unicode without translation (or, depending on how you look at it, by
-implicitly assuming that the byte strings are in Latin-1). As perl assumes
-the C locale by default, upgrading a string to UTF-8 may change the
-meaning of its contents regarding character classes, case mapping, etc.
-This should probably emit a warning (at least).
+one should now write
 
-=head2 UTF8 caching code
+    FILE* f;
+    errno_t err = fopen_s(&f, __FILE__, "r"); 
 
-The string position/offset cache is not optional. It should be.
+Currently, the warnings about these deprecations have been disabled by adding
+-D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that
+warning suppressant and actually make use of the new secure CRT functions.
+
+There is also a similar issue with POSIX CRT function names like fileno having
+been deprecated in favour of ISO C++ conformant names like _fileno. These
+warnings are also currently suppressed with the compiler option /wd4996. It
+might be nice to do as Microsoft suggest here too, although, unlike the secure
+functions issue, there is presumably little or no benefit in this case.
+
+=head1 Tasks that need a knowledge of XS
+
+These tasks would need C knowledge, and roughly the level of knowledge of
+the perl API that comes from writing modules that use XS to interface to
+C.
+
+=head2 autovivification
+
+Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
+
+This task is incremental - even a little bit of work on it will help.
 
 =head2 Unicode in Filenames
 
@@ -110,196 +455,222 @@ L<perlrun>.)
 
 Currently the %ENV entries are always byte strings.
 
-=head1 Regexps
+=head2 Unicode and glob()
 
-=head2 regexp optimiser optional
+Currently glob patterns and filenames returned from File::Glob::glob()
+are always byte strings.
 
-The regexp optimiser is not optional. It should configurable to be, to allow
-its performance to be measured, and its bugs to be easily demonstrated.
+=head2 use less 'memory'
 
-=head2 common suffices/prefices in regexps (trie optimization)
+Investigate trade offs to switch out perl's choices on memory usage.
+Particularly perl should be able to give memory back.
 
-Currently, the user has to optimize C<foo|far> and C<foo|goo> into
-C<f(?:oo|ar)> and C<[fg]oo> by hand; this could be done automatically.
+This task is incremental - even a little bit of work on it will help.
 
-=head1 POD
+=head2 Re-implement C<:unique> in a way that is actually thread-safe
 
-=head2 POD -> HTML conversion still sucks
+The old implementation made bad assumptions on several levels. A good 90%
+solution might be just to make C<:unique> work to share the string buffer
+of SvPVs. That way large constant strings can be shared between ithreads,
+such as the configuration information in F<Config>.
 
-Which is crazy given just how simple POD purports to be, and how simple HTML
-can be.
+=head2 Make tainting consistent
 
-=head1 Misc medium sized projects
+Tainting would be easier to use if it didn't take documented shortcuts and
+allow taint to "leak" everywhere within an expression.
 
-=head2 UNITCHECK
+=head2 readpipe(LIST)
 
-Introduce a new special block, UNITCHECK, which is run at the end of a
-compilation unit (module, file, eval(STRING) block). This will correspond to
-the Perl 6 CHECK. Perl 5's CHECK cannot be changed or removed because the
-O.pm/B.pm backend framework depends on it.
+system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
+running a shell. readpipe() (the function behind qx//) could be similarly
+extended.
 
-=head2 optional optimizer
+=head2 strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf()
 
-Make the peephole optimizer optional.
+Maybe create a utility that checks after each libperl.a creation that
+none of the above (nor sprintf(), vsprintf(), or *SHUDDER* gets())
+ever creep back to libperl.a.
 
-=head2 You WANT *how* many
+  nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/; print "$o $F[1]" if $F[0] eq "U" && $F[1] =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/'
 
-Currently contexts are void, scalar and list. split has a special mechanism in
-place to pass in the number of return values wanted. It would be useful to
-have a general mechanism for this, backwards compatible and little speed hit.
-This would allow proposals such as short circuiting sort to be implemented
-as a module on CPAN.
+Note, of course, that this will only tell whether B<your> platform
+is using those naughty interfaces.
 
-=head2 lexical aliases
+=head2 Audit the code for destruction ordering assumptions
 
-Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>.
+Change 25773 notes
 
-=head2 no 6
+    /* Need to check SvMAGICAL, as during global destruction it may be that
+       AvARYLEN(av) has been freed before av, and hence the SvANY() pointer
+       is now part of the linked list of SV heads, rather than pointing to
+       the original body.  */
+    /* FIXME - audit the code for other bugs like this one.  */
 
-Make C<no 6> and C<no v6> work (opposite of C<use 5.005>, etc.).
+adding the C<SvMAGICAL> check to
 
-=head2 IPv6
+    if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) {
+        MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen);
 
-Clean this up. Check everything in core works
+Go through the core and look for similar assumptions that SVs have particular
+types, as all bets are off during global destruction.
 
-=head2 entersub XS vs Perl
+=head2 Extend PerlIO and PerlIO::Scalar
 
-At the moment pp_entersub is huge, and has code to deal with entering both
-perl and and XS subroutines. Subroutine implementations rarely change between 
-perl and XS at run time, so investigate using 2 ops to enter subs (one for
-XS, one for perl) and swap between if a sub is redefined.
+PerlIO::Scalar doesn't know how to truncate().  Implementing this
+would require extending the PerlIO vtable.
 
-=head2 @INC source filter to Filter::Simple
+Similarly the PerlIO vtable doesn't know about formats (write()), or
+about stat(), or chmod()/chown(), utime(), or flock().
 
-The second return value from a sub in @INC can be a source filter. This isn't
-documented. It should be changed to use Filter::Simple, tested and documented.
+(For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership
+would mean.)
 
-=head2 bincompat functions
+PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(),
+opendir(), closedir(), seekdir(), rewinddir(), glob(); symlink(),
+readlink().
 
-There are lots of functions which are retained for binary compatibility.
-Clean these up. Move them to mathom.c, and don't compile for blead?
+=head2 -C on the #! line
 
-=head2 Use fchown/fchmod internally
+It should be possible to make -C work correctly if found on the #! line,
+given that all perl command line options are strict ASCII, and -C changes
+only the interpretation of non-ASCII characters, and not for the script file
+handle. To make it work needs some investigation of the ordering of function
+calls during startup, and (by implication) a bit of tweaking of that order.
 
-The old perltodo notes "This has been done in places, but needs a thorough
-code review. Also fchdir is available in some platforms."
 
-=head1 Tests
+=head1 Tasks that need a knowledge of the interpreter
 
-=head2 Make Schwern poorer
+These tasks would need C knowledge, and knowledge of how the interpreter works,
+or a willingness to learn.
 
-Tests for everything, At which point Schwern coughs up $500 to TPF.
+=head2 Implement $value ~~ 0 .. $range
 
-=head2 test B
+It would be nice to extend the syntax of the C<~~> operator to also
+understand numeric (and maybe alphanumeric) ranges.
 
-A test suite for the B module would be nice.
+=head2 Attach/detach debugger from running program
 
-=head2 Improve tests for Config.pm
+The old perltodo notes "With C<gdb>, you can attach the debugger to a running
+program if you pass the process ID. It would be good to do this with the Perl
+debugger on a running Perl program, although I'm not sure how it would be
+done." ssh and screen do this with named pipes in /tmp. Maybe we can too.
 
-Config.pm doesn't appear to be well tested.
+=head2 LVALUE functions for lists
 
-=head2 common test code for timed bailout
+The old perltodo notes that lvalue functions don't work for list or hash
+slices. This would be good to fix.
 
-Write portable self destruct code for tests to stop them burning CPU in
-infinite loops. Needs to avoid using alarm, as some of the tests are testing
-alarm/sleep or timers.
+=head2 LVALUE functions in the debugger
 
-=head1 Installation
+The old perltodo notes that lvalue functions don't work in the debugger. This
+would be good to fix.
 
-=head2 compressed man pages
+=head2 regexp optimiser optional
 
-Be able to install them
+The regexp optimiser is not optional. It should configurable to be, to allow
+its performance to be measured, and its bugs to be easily demonstrated.
 
-=head2 Make Config.pm cope with differences between build and installed perl
+=head2 delete &function
 
-=head2 Relocatable perl
+Allow to delete functions. One can already undef them, but they're still
+in the stash.
 
-Make it possible to create a relocatable perl binary. Will need some collusion
-with Config.pm. We could use a syntax of ... for location of current binary?
+=head2 optional optimizer
 
-=head2 make HTML install work
+Make the peephole optimizer optional. Currently it performs two tasks as
+it walks the optree - genuine peephole optimisations, and necessary fixups of
+ops. It would be good to find an efficient way to switch out the
+optimisations whilst keeping the fixups.
 
-=head2 put patchlevel in -v
+=head2 You WANT *how* many
 
-Currently perl from p4/rsync ships with a patchlevel.h file that usually
-defines one local patch, of the form "MAINT12345" or "RC1". The output of
-perl -v doesn't report that a perl isn't an official release, and this
-information can get lost in bugs reports. Because of this, the minor version
-isn't bumped up until RC time, to minimise the possibility of versions of perl
-escaping that believe themselves to be newer than they actually are.
+Currently contexts are void, scalar and list. split has a special mechanism in
+place to pass in the number of return values wanted. It would be useful to
+have a general mechanism for this, backwards compatible and little speed hit.
+This would allow proposals such as short circuiting sort to be implemented
+as a module on CPAN.
 
-It would be useful to find an elegant way to have the "this is an interim
-maintenance release" or "this is a release candidate" in the terse -v output,
-and have it so that it's easy for the pumpking to remove this just as the
-release tarball is rolled up. This way the version pulled out of rsync would
-always say "I'm a development release" and it would be safe to bump the
-reported minor version as soon as a release ships, which would aid perl
-developers.
+=head2 lexical aliases
 
-=head1 Incremental things
+Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>.
 
-Some tasks that don't need to get done in one big hit.
+=head2 entersub XS vs Perl
 
-=head2 autovivification
+At the moment pp_entersub is huge, and has code to deal with entering both
+perl and XS subroutines. Subroutine implementations rarely change between 
+perl and XS at run time, so investigate using 2 ops to enter subs (one for
+XS, one for perl) and swap between if a sub is redefined.
 
-Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
+=head2 Self ties
 
-=head2 fix tainting bugs
+self ties are currently illegal because they caused too many segfaults. Maybe
+the causes of these could be tracked down and self-ties on all types re-
+instated.
 
-Fix the bugs revealed by running the test suite with the C<-t> switch (via
-C<make test.taintwarn>).
+=head2 Optimize away @_
 
-=head2 Make tainting consistent
+The old perltodo notes "Look at the "reification" code in C<av.c>".
 
-Tainting would be easier to use if it didn't take documented shortcuts and allow
-taint to "leak" everywhere within an expression.
+=head2 What hooks would assertions need?
 
-=head2 Dual life everything
+Assertions are in the core, and work. However, assertions needed to be added
+as a core patch, rather than an XS module in ext, or a CPAN module, because
+the core has no hooks in the necessary places. It would be useful to
+investigate what hooks would need to be added to make it possible to provide
+the full assertion support from a CPAN module, so that we aren't constraining
+the imagination of future CPAN authors.
 
-As part of the "dists" plan, anything that doesn't belong in the smallest perl
-distribution needs to be dual lifed. Anything else can be too.
+=head2 Properly Unicode safe tokeniser and pads.
 
-=head1 Vague things
+The tokeniser isn't actually very UTF-8 clean. C<use utf8;> is a hack -
+variable names are stored in stashes as raw bytes, without the utf-8 flag
+set. The pad API only takes a C<char *> pointer, so that's all bytes too. The
+tokeniser ignores the UTF-8-ness of C<PL_rsfp>, or any SVs returned from
+source filters.  All this could be fixed.
 
-Some more nebulous ideas
+=head2 The yada yada yada operators
 
-=head2 threads
+Perl 6's Synopsis 3 says:
 
-Make threads more robust.
+I<The ... operator is the "yada, yada, yada" list operator, which is used as
+the body in function prototypes. It complains bitterly (by calling fail)
+if it is ever executed. Variant ??? calls warn, and !!! calls die.>
 
-=head2 POSIX memory footprint
+Those would be nice to add to Perl 5. That could be done without new ops.
 
-Ilya observed that use POSIX; eats memory like there's no tomorrow, and at
-various times worked to cut it down. There is probably still fat to cut out -
-for example POSIX passes Exporter some very memory hungry data structures.
+=head1 Big projects
 
-=head2 Optimize away @_
+Tasks that will get your name mentioned in the description of the "Highlights
+of 5.10"
 
-The old perltodo notes "Look at the "reification" code in C<av.c>".
+=head2 make ithreads more robust
 
-=head2 switch ops
+Generally make ithreads more robust. See also L</iCOW>
 
-The old perltodo notes "Although we have C<Switch.pm> in core, Larry points to
-the dormant C<nswitch> and C<cswitch> ops in F<pp.c>; using these opcodes would
-be much faster."
+This task is incremental - even a little bit of work on it will help, and
+will be greatly appreciated.
 
-=head2 Attach/detach debugger from running program
+One bit would be to write the missing code in sv.c:Perl_dirp_dup.
 
-The old perltodo notes "With C<gdb>, you can attach the debugger to a running
-program if you pass the process ID. It would be good to do this with the Perl
-debugger on a running Perl program, although I'm not sure how it would be done."
-ssh and screen do this with named pipes in tmp. Maybe we can too.
+Fix Perl_sv_dup, et al so that threads can return objects.
 
-=head2 A decent benchmark
+=head2 iCOW
 
-perlbench seems impervious to any recent changes made to the perl core. It would
-be useful to have a reasonable general benchmarking suite that roughly
-represented what current perl programs do, and measurably reported whether
-tweaks to the core improve, degrade or don't really affect performance, to
-guide people attempting to optimise the guts of perl.
+Sarathy and Arthur have a proposal for an improved Copy On Write which
+specifically will be able to COW new ithreads. If this can be implemented
+it would be a good thing.
 
-=head2 readpipe(LIST)
+=head2 (?{...}) closures in regexps
 
-system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
-running a shell. readpipe() (the function behind qx//) could be similarly
-extended.
+Fix (or rewrite) the implementation of the C</(?{...})/> closures.
+
+=head2 A re-entrant regexp engine
+
+This will allow the use of a regex from inside (?{ }), (??{ }) and
+(?(?{ })|) constructs.
+
+=head2 Add class set operations to regexp engine
+
+Apparently these are quite useful. Anyway, Jeffery Friedl wants them.
+
+demerphq has this on his todo list, but right at the bottom.