This seems to do what you want:

use warnings;
use strict;

my $string = 'blah/blah/blah#ThisIsWhatIWant?ButNotThisEtc';

if( $string =~ m/#([^?]*)/ )
{
    print "matched -->$1<--\n";
}
[download]

Output:

matched -->ThisIsWhatIWant<--
[download]

This looks like a URL, though, and I wonder if something from CPAN would do the trick. Perhaps another monk knows of a module.

Update: YAPE::Regex::Explain is a handy little module that will take a regex and produce a human-readable explanation of it. For example,

use YAPE::Regex::Explain;

my $re = qr/#([^?]*)/;
my $p = YAPE::Regex::Explain->new($re)->explain;
print "$p\n";
[download]

Output:

The regular expression:

(?-imsx:#([^?]*))

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  #                        '#'
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    [^?]*                    any character except: '?' (0 or more
                             times (matching the most amount
                             possible))
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
[download]

You could use this (as well as perlre) to help yourself understand why the regexen you initially tried weren't working as you expected. Trying things at random can be one way to learn how things work, but in the end Don't Program by Coincidence. :-)

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