Here is what I use sometimes, which is not perfect as you can't use brackets inside a regexp, I have to add level counting (comments and patches welcome!). You could also have a look at Regexp::Common::Balanced.

#!/bin/perl -w
use strict;

my %brace=( '[' => ']', '(' =>')', '{' => '}', '<' => '>');
my $not_brace_class= '[^\\' . join( '\\', keys %brace) . ']';

my $SIMPLE_REGEXP = "(($not_brace_class)(?:(\\\\.|.)*?)\\2)";

my @regexp= ($SIMPLE_REGEXP);
while( my( $open, $close)= each( %brace))
  { push @regexp, "(\\$open(?:\\\\.|.)*?\\$close)"; }


while( <DATA>)
  { chomp;
    my( $exp, $expected_match)= split /\t+/;
    print "$exp: ";
    foreach my $regexp (@regexp)
      { if( $exp=~ m{^$regexp}) 
          { my $found= $1; 
            if( $found eq $expected_match) 
          { print "REGEXP OK "; }
        else
          { print "REGEXP matches $found instead of $expected_match (r
+egexp is $regexp)"; }
        last;
      }
      }
    print "\n";
  }

__DATA__
/toto/        /toto/
#toto#        #toto#
{toto}        {toto}
/to\to/        /to\to/
/to\/to/    /to\/to/
#to\to#        #to\to#
#to\#to#    #to\#to#
[to\to]        [to\to]
[to\]to]    [to\]to]
[to[to]]    [to[to]]
/toto/no    /toto/
#toto#no    #toto#
{toto}no    {toto}
/to\to/no    /to\to/
/to\/to/no    /to\/to/
#to\to#no    #to\to#
#to\#to#no    #to\#to#
[to\to]no    [to\to]
[to\]to]no    [to\]to]
[to[to]]no    [to[to]]
/toto/no/    /toto/
#toto#no#    #toto#
{toto}no{no    {toto}
{toto}no{}no    {toto}
{toto}no}no    {toto}
{toto}no{    {toto}
{toto}no{}    {toto}
{toto}no}    {toto}
/to\to/no/    /to\to/
/to\to/no\/    /to\to/
/to\/to/no/    /to\/to/
#to\to#no\#    #to\to#
#to\#to#no#    #to\#to#
[to\to]no[    [to\to]
[to\]to]no]    [to\]to]
[to[to]]no[]    [to[to]]
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