new-style regexps

[p5pRT]

Migrated from rt.perl.org#3461 (status was 'resolved')

Searchable as RT3461$

[p5pRT]

From [email protected]

This appears to be a bug involving new-style patterns for
regular expressions when put in a variable.

----------------------- perl script​:

#!/usr/bin/perl

$a = 'error-free';
$old = '[\.\+\-\*]';
$new = '[\Q.+-*\E]';
print "1\n" if $a =~ /[\.\+\-\*]/;
print "2\n" if $a =~ /$old/;
print "3\n" if $a =~ /[\Q.+-*\E]/x;
print "4\n" if $a =~ /$new/x;

----------------------- output​:

1
2
3
/[\Q.+-*\E]/​: invalid [] range in regexp at try line 9.

----------------------- from perl -V​:

Summary of my perl5 (5.0 patchlevel 5 subversion 3) configuration​:
  Platform​:
  osname=linux, osvers=2.2.5-</font> </b>smp, archname=i386-linux
  uname='linux porky.devel.redhat.com 2.2.5-</font> </b>smp #1 smp wed jun 2 09​:<font color=blue> <b>​:51 edt 1999 i686 unknown '
  hint=recommended, useposix=true, d_sigaction=define
  usethreads=undef useperlio=undef d_sfio=undef
  Compiler​:
  cc='cc', optimize='-O2 -m486 -fno-strength-reduce', gccversion=egcs-2.91.66 19990314/Linux (egcs-1.1.2 release) cppflags='-Dbool=char -DHAS_BOOL -I/usr/local/include'
  ccflags ='-Dbool=char -DHAS_BOOL -I/usr/local/include'
  stdchar='char', d_stdstdio=undef, usevfork=false
  intsize=4, longsize=4, ptrsize=4, doublesize=8
  d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
  alignbytes=4, usemymalloc=n, prototype=define
  Linker and Libraries​:
  ld='cc', ldflags =' -L/usr/local/lib'
  libpth=/usr/local/lib /lib /usr/lib
  libs=-lnsl -ldl -lm -lc -lposix -lcrypt
  libc=, so=so, useshrplib=false, libperl=libperl.a
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic'
  cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib'

Characteristics of this binary (from libperl)​:
  Built under linux
  Compiled at Feb 2 2000 15​:35​:58
  @​INC​:
  /usr/lib/perl5/5.00503/i386-linux
  /usr/lib/perl5/5.00503
  /usr/lib/perl5/site_perl/5.005/i386-linux
  /usr/lib/perl5/site_perl/5.005
  .

[p5pRT]

From @mjdominus

This appears to be a bug involving new-style patterns for
regular expressions when put in a variable.

In your example, you have

$new = '[\Q.+-*\E]';
print "4\n" if $a =~ /$new/x;

The regex does not contain any \Q..\E sequences, so no quotemeta
operation is performed. Data, once interpolated, is not examined for
metacharacters; it is always interpolated literally. For example​:

  $foo = 4;
  $bar = '$foo';
  $baz = "-$bar-"

does not set $baz to '-4-'.

This is normally what you want. Consider this example​:

  print "Enter your name​: ";
  chomp($name = <STDIN>);
  print "Hello, $name!";

Suppose the user enters the string

  \Q

You would (or should) expect the output to be

  Hello, \Q!

and it would be extremely bizarre for this program to print

  Hello, \!

instead. But this is what you are asking for.

The section "Gory details of parsing quoted constructs" in perlop
discusses this in more detail.