perltodo - Perl TO-DO List
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:
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/
=head1 To do during 5.6.x
=head2 Support for I/O disciplines
C<perlio> provides this, but the interface could be a lot more
When the lexer sees, for instance, C<bytes::length>, it should
automatically load the C<bytes> pragma.
=head2 Make "\u{XXXX}" et al work
Danger, Will Robinson! Discussing the semantics of C<"\x{F00}">,
C<"\xF00"> and C<"\U{F00}"> on P5P I<will> lead to a long and boring
=head2 Create a char *sv_pvprintify(sv, STRLEN *lenp, UV flags)
For displaying PVs with control characters, embedded nulls, and Unicode.
This would be useful for printing warnings, or data and regex dumping,
not_a_number(), and so on.
Requirements: should handle both byte and UTF8 strings. isPRINT()
characters printed as-is, character less than 256 as \xHH, Unicode
characters as \x{HHH}. Don't assume ASCII-like, either, get somebody
on EBCDIC to test the output.
Possible options, controlled by the flags:
- whitespace (other than ' ' of isPRINT()) printed as-is
- use isPRINT_LC() instead of isPRINT()
- print control characters like this: "\cA"
- print control characters like this: "^A"
- non-PRINTables printed as '.' instead of \xHH
- use \OOO instead of \xHH
- use the C/Perl-metacharacters like \n, \t
- have a maximum length for the produced string (read it from *lenp)
- append a "..." to the produced string if the maximum length is exceeded
- really fancy: print unicode characters as \N{...}
NOTE: pv_display(), pv_uni_display(), sv_uni_display() are already
doing something like the above.
=head2 Overloadable regex assertions
This may or may not be possible with the current regular expression
engine. The idea is that, for instance, C<\b> needs to be
algorithmically computed if you're dealing with Thai text. Hence, the
B<\b> assertion wants to be overloaded by a function.
Allow for long form of the General Category Properties, e.g
C<\p{IsOpenPunctuation}>, not just the abbreviated form, e.g.
Allow for the metaproperties: C<XID Start>, C<XID Continue>,
C<NF*_NO>, C<NF*_MAYBE> (require the DerivedCoreProperties and
DerviceNormalizationProperties files).
There are also multiple value properties still unimplemented:
C<Numeric Type>, C<East Asian Width>.
Case Mappings? http://www.unicode.org/unicode/reports/tr21/
Mostly implemented (all of 1:1, 1:N, N:1), only the "final sigma"
and locale-specific rules of SpecCase are not implemented.
UTF-8 identifier names should probably be canonicalized: NFC?
UTF-8 in package names and sub names? The first is problematic
because of the mapping to pathnames, ditto for the second one if
one does autosplitting, for example. Some of this works already
in 5.8.0, but essentially it is unsupported. Constructs to consider,
sub new { bless {}, shift };
sub UnicodeMethod1 { ... $_[0]->UnicodeMethod2(...) ... }
sub UnicodeMethod2 { ... } # in here caller(0) should contain Unicode
my $x = UnicodePackage->new;
print ref $x, "\n"; # should be Unicode
my $y = UnicodeMethod3 UnicodePackage ...;
In the above all I<UnicodeXxx> contain (identifier-worthy) characters
beyond the code point 255, for example 256. Wherever package/class or
subroutine names can be returned needs to be checked for Unicodeness.
See L<perlunicode/UNICODE REGULAR EXPRESSION SUPPORT LEVEL> for what's
there and what's missing. Almost all of Levels 2 and 3 is missing,
and as of 5.8.0 not even all of Level 1 is there.
They have some tricks Perl doesn't yet implement, such as character
http://www.unicode.org/unicode/reports/tr18/
=head2 Work out exit/die semantics for threads
There are some suggestions to use for example something like this:
default to "(thread exiting first will) wait for the other threads
until up to 60 seconds". Other possibilities:
use threads wait_for => 10;
use threads wait_for => -1;
http://archive.develooper.com/perl5-porters@perl.org/msg79618.html
=head2 Better support for nonpreemptive threading systems like GNU pth
To better support nonpreemptive threading systems, perhaps some of the
blocking functions internally in Perl should do a yield() before a
blocking call. (Now certain threads tests ({basic,list,thread.t})
simply do a yield() before they sleep() to give nonpreemptive thread
implementations a chance).
In some cases, like the GNU pth, which has replacement functions that
are nonblocking (pth_select instead of select), maybe Perl should be
using them instead when built for threading.
=head2 Typed lexicals for compiler
=head2 Compiler workarounds for Win32
=head2 AUTOLOADing in the compiler
=head2 Fixing comppadlist when compiling
=head2 Cleaning up exported namespace
=head2 Complete signal handling
Add C<PERL_ASYNC_CHECK> to opcodes which loop; replace C<sigsetjmp> with
C<sigjmp>; check C<wait> for signal safety.
=head2 Out-of-source builds
This was done for 5.6.0, but needs reworking for 5.7.x
=head2 POSIX realtime support
POSIX 1003.1 1996 Edition support--realtime stuff: POSIX semaphores,
message queues, shared memory, realtime clocks, timers, signals (the
metaconfig units mostly already exist for these)
Reader-writer locks, realtime/asynchronous IO
There are non-core modules, such as C<Socket6>, but these will need
integrating when IPv6 actually starts to really happen. See RFC 2292
=head2 Long double conversion
Floating point formatting is still causing some weird test failures.
Locales and Unicode interact with each other in unpleasant ways.
One possible solution would be to adopt/support ICU:
http://oss.software.ibm.com/developerworks/opensource/icu/project/
=head2 Arithmetic on non-Arabic numerals
C<[1234567890]> aren't the only numerals any more.
=head2 POSIX Unicode character classes
(C<[=a=]> for equivalence classes, C<[.ch.]> for collation.)
These are dependent on Unicode normalization and collation.
=head2 Factoring out common suffices/prefices in regexps (trie optimization)
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.
=head2 Security audit shipped utilities
All the code we ship with Perl needs to be sensible about temporary file
handling, locking, input validation, and so on.
=head2 Sort out the uid-setting mess
Currently there are several problems with the setting of uids ($<, $>
for the real and effective uids). Firstly, what exactly setuid() call
gets invoked in which platform is simply a big mess that needs to be
untangled. Secondly, the effects are apparently not standard across
platforms, (if you first set $< and then $>, or vice versa, being
uid == euid == zero, or just euid == zero, or as a normal user, what are
the results?). The test suite not (usually) being run as root means
that these things do not get much testing. Thirdly, there's quite
often a third uid called saved uid, and Perl has no knowledge of that
feature in any way. (If one has the saved uid of zero, one can get
back any real and effective uids.) As an example, to change also the
saved uid, one needs to set the real and effective uids B<twice>-- in
most systems, that is: in HP-UX that doesn't seem to work.
Have a way to introduce user-defined opcodes without the subroutine call
overhead of an XSUB; the user should be able to create PP code. Simon
Cozens has some ideas on this.
Windows needs a way to know what version of an XS or C<libperl> DLL it's
=head2 Introduce @( and @)
C<$(> may return "foo bar baz". Unfortunately, since groups can
theoretically have spaces in their names, this could be one, two or
=head2 Floating point handling
C<NaN> and C<inf> support is particularly troublesome.
(fp_classify(), fp_class(), fp_class_d(), class(), isinf(),
isfinite(), finite(), isnormal(), unordered(), <ieeefp.h>,
<fp_class.h> (there are metaconfig units for all these) (I think),
fp_setmask(), fp_getmask(), fp_setround(), fp_getround()
(no metaconfig units yet for these). Don't forget finitel(), fp_classl(),
fp_class_l(), (yes, both do, unfortunately, exist), and unorderedl().)
As of Perl 5.6.1, there is a Perl macro, Perl_isnan().
=head2 IV/UV preservation
Nicholas Clark has done a lot of work on this, but work is continuing.
C<+>, C<-> and C<*> work, but guards need to be in place for C<%>, C</>,
C<&>, C<oct>, C<hex> and C<pack>.
=head2 Replace pod2html with something using Pod::Parser
The CPAN module C<Marek::Pod::Html> may be a more suitable basis for a
C<pod2html> converter; the current one duplicates the functionality
abstracted in C<Pod::Parser>, which makes updating the POD language
=head2 Automate module testing on CPAN
When a new Perl is being beta tested, porters have to manually grab
their favourite CPAN modules and test them - this should be done
=head2 sendmsg and recvmsg
We have all the other BSD socket functions but these. There are
metaconfig units for these functions which can be added. To avoid these
being new opcodes, a solution similar to the way C<sockatmark> was added
would be preferable. (Autoload the C<IO::whatever> module.)
=head2 Rewrite perlre documentation
The new-style patterns need full documentation, and the whole document
needs to be a lot clearer.
=head2 Convert example code to IO::Handle filehandles
=head2 Document Win32 choices
=head2 Make roffitall find pods and libs itself
Simon Cozens has done some work on this but it needs a rethink.
=head1 To do at some point
These are ideas that have been regularly tossed around, that most
people believe should be done maybe during 5.8.x
=head2 Remove regular expression recursion
Because the regular expression engine is recursive, badly designed
expressions can lead to lots of recursion filling up the stack. Ilya
claims that it is easy to convert the engine to being iterative, but
this has still not yet been done. There may be a regular expression
engine hit squad meeting at TPC5.
=head2 Memory leaks after failed eval
Perl will leak memory if you C<eval "hlagh hlagh hlagh hlagh">. This is
partially because it attempts to build up an op tree for that code and
doesn't properly free it. The same goes for non-syntactically-correct
regular expressions. Hugo looked into this, but decided it needed a
mark-and-sweep GC implementation.
Alan notes that: The basic idea was to extend the parser token stack
(C<YYSTYPE>) to include a type field so we knew what sort of thing each
element of the stack was. The F<perly.c> code would then have to be
postprocessed to record the type of each entry on the stack as it was
created, and the parser patched so that it could unroll the stack
This is possible to do, but would be pretty messy to implement, as it
would rely on even more sed hackery in F<perly.fixer>.
Make Perl buildable with a cross-compiler. This will play havoc with
Configure, which needs to know how the target system will respond to
its tests; maybe C<microperl> will be a good starting point here.
(Indeed, Bart Schuller reports that he compiled up C<microperl> for
the Agenda PDA and it works fine.) A really big spanner in the works
is the bootstrapping build process of Perl: if the filesystem the
target systems sees is not the same what the build host sees, various
input, output, and (Perl) library files need to be copied back and forth.
As of 5.8.0 Configure mostly works for cross-compilation
(used successfully for iPAQ Linux), miniperl gets built,
but then building DynaLoader (and other extensions) fails
since MakeMaker knows nothing of cross-compilation.
(See INSTALL/Cross-compilation for the state of things.)
=head2 Perl preprocessor / macros
Source filters help with this, but do not get us all the way. For
instance, it should be possible to implement the C<??> operator somehow;
source filters don't (quite) cut it.
=head2 Perl lexer in Perl
Damian Conway is planning to work on this, but it hasn't happened yet.
=head2 Using POSIX calls internally
When faced with a BSD vs. SysV -style interface to some library or
system function, perl's roots show in that it typically prefers the BSD
interface (but falls back to the SysV one). One example is getpgrp().
Other examples include C<memcpy> vs. C<bcopy>. There are others, mostly in
Mostly, this item is a suggestion for which way to start a journey into
an C<#ifdef> forest. It is not primarily a suggestion to eliminate any of
POSIX calls are perhaps more likely to be portable to unexpected
architectures. They are also perhaps more likely to be actively
maintained by a current vendor. They are also perhaps more likely to be
available in thread-safe versions, if appropriate.
=head2 -i rename file when changed
It's only necessary to rename a file when inplace editing when the file
has changed. Detecting a change is perhaps the difficult bit.
=head2 All ARGV input should act like E<lt>E<gt>
eg C<read(ARGV, ...)> doesn't currently read across multiple files.
=head2 Support for rerunning debugger
There should be a way of restarting the debugger on demand.
=head2 Test Suite for the Debugger
The debugger is a complex piece of software and fixing something
here may inadvertently break something else over there. To tame
this chaotic behaviour, a test suite is necessary.
The basic principle is sound, but there are problems with the semantics
of self-referential and mutually referential lexical subs: how to
=head2 One-pass global destruction
Sweeping away all the allocated memory in one go is a laudable goal, but
it's difficult and in most cases, it's easier to let the memory get
=head2 Rewrite regexp parser
There has been talk recently of rewriting the regular expression parser
to produce an optree instead of a chain of opcodes; it's unclear whether
or not this would be a win.
=head2 Cache recently used regexps
C<qr//> already gives us a way of saving compiled regexps, but it should
=head2 Cross-compilation support
Bart Schuller reports that using C<microperl> and a cross-compiler, he
got Perl working on the Agenda PDA. However, one cannot build a full
Perl because Configure needs to get the results for the target platform,
=head2 Bit-shifting bitvectors
and have the 999'th bit set.
Currently if you try with shift bitvectors you shift the NV/UV, instead
of the bits in the PV. Not very logical.
The debugger is implemented in Perl in F<perl5db.pl>; turning it into a
pragma should be easy, but making it work lexically might be more
difficult. Fiddling with C<$^P> would be necessary.
Identify areas where speed/memory tradeoffs can be made and have a hint
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
=head2 Shrink opcode tables
Look at the "reification" code in C<av.c>
=head2 Prototypes versus indirect objects
Currently, indirect object syntax bypasses prototype checks.
HTML versions of the documentation need to be installed by default; a
call to C<installhtml> from C<installperl> may be all that's necessary.
=head2 Prototype method calls
=head2 Return context prototype declarations
=head2 Garbage collection
There have been persistent mumblings about putting a mark-and-sweep
garbage detector into Perl; Alan Burlison has some ideas about this.
Mark-Jason Dominus has the beginnings of one of these.
There are a few suggestions for what to do with C<perldoc>: maybe a
full-text search, an index function, locating pages on a particular
high-level subject, and so on.
=head2 Install .3p manpages
This is a bone of contention; we can create C<.3p> manpages for each
built-in function, but should we install them by default? Tcl does this,
and it clutters up C<apropos>.
Simon Cozens promises to do this before he gets old.
=head2 Update POSIX.pm for 1003.1-2
=head2 Retargetable installation
Allow C<@INC> to be changed after Perl is built.
=head2 POSIX emulation on non-POSIX systems
Make C<POSIX.pm> behave as POSIXly as possible everywhere, meaning we
have to implement POSIX equivalents for some functions if necessary.
=head2 Rename Win32 headers
=head2 Finish off lvalue functions
They don't work in the debugger, and they don't work for list or hash
=head2 Update sprintf documentation
Hugo van der Sanden plans to look at this.
=head2 Use fchown/fchmod internally
This has been done in places, but needs a thorough code review.
Also fchdir is available in some platforms.
=head2 Make v-strings overloaded objects
Instead of having to guess whether a string is a v-string and thus
needs to be displayed with %vd, make v-strings (readonly) objects
(class "vstring"?) with a stringify overload.
=head2 Allow restricted hash assignment
Currently you're not allowed to assign to a restricted hash at all,
%restricted = (foo => 42); # error
This should be allowed if the new keyset is a subset of the old
keyset. May require more extra code than we'd like in pp_aassign.
=head2 Should overload be inheritable?
Should overload be 'contagious' through @ISA so that derived classes
would inherit their base classes' overload definitions? What to do
in case of overload conflicts?
Should taint be stopped from affecting control flow, if ($tainted)?
Should tainted symbolic method calls and subref calls be stopped?
(Look at Ruby's $SAFE levels for inspiration?)
Ideas which have been discussed, and which may or may not happen.
=head2 ref() in list context
It's unclear what this should do or how to do it without breaking old
=head2 Make tr/// return histogram of characters in list context
There is a patch for this, but it may require Unicodification.
=head2 Compile to real threaded code
=head2 Modifiable $1 et al.
($x = "elephant") =~ /e(ph)/;
$1 = "g"; # $x = "elegant"
What happens if there are multiple (nested?) brackets? What if the
string changes between the match and the assignment?
=head2 Procedural interfaces for IO::*, etc.
Some core modules have been accused of being overly-OO. Adding
procedural interfaces could demystify them.
=head2 Attach/detach debugger from running program
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.
A non-core module that would use "native" GUI to create graphical
=head2 foreach(reverse ...)
foreach (reverse @_) { ... }
puts C<@_> on the stack, reverses it putting the reversed version on the
stack, then iterates forwards. Instead, it could be special-cased to put
C<@_> on the stack then iterate backwards.
=head2 Constant function cache
=head2 Approximate regular expression matching
These items B<always> need doing:
=head2 Update guts documentation
Simon Cozens tries to do this when possible, and contributions to the
C<perlapi> documentation is welcome.
Michael Schwern will donate $500 to Yet Another Society when all core
=head2 Update auxiliary tools
The code we ship with Perl should look like good Perl 5.
=head2 Create debugging macros
Debugging macros (like printsv, dump) can make debugging perl inside a
C debugger much easier. A good set for gdb comes with mod_perl.
Something similar should be distributed with perl.
The proper way to do this is to use and extend Devel::DebugInit.
Devel::DebugInit also needs to be extended to support threads.
See p5p archives for late May/early June 2001 for a recent discussion
=head2 truncate to the people
One can emulate ftruncate() using F_FREESP and F_CHSIZ fcntls
(see the UNIX FAQ for details). This needs to go somewhere near
One can emulate truncate() easily if one has ftruncate().
This emulation should also go near pp_sys.pp_truncate().
=head2 Unicode in Filenames
chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open,
opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen,
system, truncate, unlink, utime. All these could potentially accept
Unicode filenames either as input or output (and in the case of system
and qx Unicode in general, as input or output to/from the shell).
Whether a filesystem - an operating system pair understands Unicode in
Known combinations that have some level of understanding include
Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac
OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to
create Unicode filenames, what forms of Unicode are accepted and used
(UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used,
and so on, varies. Finding the right level of interfacing to Perl
requires some thought. Remember that an OS does not implicate a
Note that in Windows the -C command line flag already does quite
a bit of the above (but even there the support is not complete:
for example the exec/spawn are not Unicode-aware) by turning on
the so-called "wide API support".
=head1 Recently done things
These are things which have been on the todo lists in previous releases
but have recently been completed.
=head2 Alternative RE syntax module
The C<Regexp::English> module, available from the CPAN, provides this:
=head2 Safe signal handling
A new signal model went into 5.7.1 without much fanfare. Operations and
C<malloc>s are no longer interrupted by signals, which are handled
between opcodes. This means that C<PERL_ASYNC_CHECK> now actually does
something. However, there are still a few things that need to be done.
Modules which implement arrays in terms of strings, substrings or files
can be found on the CPAN.
C<Time::HiRes> has been integrated into the core.
=head2 setitimer and getimiter
Adding C<Time::HiRes> got us this too.
=head2 Testing __DIE__ hook
=head2 CPP equivalent in Perl
A C Yardley will probably have done this by the time you can read this.
This allows for a generalization of the C constant detection used in
=head2 Explicit switch statements
C<Switch.pm> has been integrated into the core to give you all manner of
C<switch...case> semantics.
Nick Ing-Simmons has made UTF-EBCDIC (UTR13) work with Perl.
EBCDIC? http://www.unicode.org/unicode/reports/tr16/
Although there are probably some small bugs to be rooted out, Jarkko
Hietaniemi has made regular expressions polymorphic between bytes and
=head2 perlcc to produce executable
C<perlcc> was recently rewritten, and can now produce standalone
=head2 END blocks saved in compiled output
=head2 Secure temporary file module
Tim Jenness' C<File::Temp> is now in core.
=head2 Integrate Time::HiRes
This module is now part of core.
Benjamin Sugars has done this.
Nick Ing-Simmons' C<perlio> supports an C<mmap> IO method.
=head2 Byte to/from UTF8 and UTF8 to/from local conversion
=head2 Add sockatmark support
=head2 Mailing list archives
http://lists.perl.org/ , http://archive.develooper.com/
Richard Foley has written the bug tracking system at http://bugs.perl.org/
Chris Nandor and Matthias Neeracher have integrated the MacPerl changes
=head2 Web "nerve center" for Perl
http://use.perl.org/ is what you're looking for.
=head2 Regular expression tutorial
C<perlretut>, provided by Mark Kvale.
=head2 Debugging Tutorial
C<perldebtut>, written by Richard Foley.
=head2 Integrate new modules
Jarkko has been integrating madly into 5.7.x
=head2 Integrate profiler
C<Devel::DProf> is now a core module.
=head2 Y2K error detection
There's a configure option to detect unsafe concatenation with "19", and
a CPAN module. (C<D'oh::Year>)
=head2 Regular expression debugger
While not part of core, Mark-Jason Dominus has written C<Rx> and has
also come up with a generalised strategy for regular expression
That's, uh, F<podchecker>
=head2 "Dynamic" lexicals
=head2 Cache precompiled modules
These are items which used to be in the todo file, but have been
deprecated for some reason.
=head2 Loop control on do{}
This would break old code; use C<do{{ }}> instead.
=head2 Lexically scoped typeglobs
Not needed now we have lexical IO handles.
Damian Conway's text formatting modules seem to be the Way To Go.
=head2 Generalised want()/caller())
Robin Houston's C<Want> module does this.
This seems to be delayed until Perl 6.
The C<File::Glob> module has been used to replace the C<glob> function.
=head2 Regression tests for suidperl
C<suidperl> is deprecated in favour of common sense.
=head2 Cached hash values
We have shared hash keys, which perform the same job.
=head2 Add compression modules
The compression modules are a little heavy; meanwhile, Nick Clark is
working on experimental pragmata to do transparent decompression on
=head2 Reorganise documentation into tutorials/references
Could not get consensus on P5P about this.
=head2 Remove distinction between functions and operators
Caution: highly flammable.
=head2 Make XS easier to use
Use C<Inline> instead, or SWIG.
=head2 Make embedding easier to use
See the Perl Power Tools. ( http://language.perl.com/ppt/ )
=head2 my $Package::variable
=head2 "or" tests defined, not truth
Suggesting this on P5P B<will> cause a boring and interminable flamewar.
=head2 "class"-based lexicals
Use flyweight objects, secure hashes or, dare I say it, pseudo-hashes instead.
(Or whatever will replace pseudohashes in 5.10.)
C<ByteLoader> covers this.
=head2 Lazy evaluation / tail recursion removal
C<List::Util> gives first() (a short-circuiting grep); tail recursion
removal is done manually, with C<goto &whoami;>. (However, MJD has
found that C<goto &whoami> introduces a performance penalty, so maybe
there should be a way to do this after all: C<sub foo {START: ... goto
=head2 Make "use utf8" the default
Because of backward compatibility this is difficult: scripts could not
contain B<any legacy eight-bit data> (like Latin-1) anymore, even in
string literals or pod. Also would introduce a measurable slowdown of
at least few percentages since all regular expression operations would
be done in full UTF-8. But if you want to try this, add
-DUSE_UTF8_SCRIPTS to your compilation flags.
=head2 Unicode collation and normalization
The Unicode::Collate and Unicode::Normalize modules
by SADAHIRO Tomoyuki have been included since 5.8.0.
Collation? http://www.unicode.org/unicode/reports/tr10/
Normalization? http://www.unicode.org/unicode/reports/tr15/
=head2 pack/unpack tutorial
Wolfgang Laun finished what Simon Cozens started.
projects / OpenSPARC-T2-DV / blob