Some other resources: perlre, perlretut, perlrecharclass, Regexp Quote-Like Operators, and Pattern Matching, Regular Expressions, and Parsing.

Also see Short, Self Contained, Correct (Compilable), Example and How to ask better questions using Test::More and sample data. For the latter, both for asking questions and for general development, maybe something like:

use warnings;
use strict;

use Test::More 'no_plan';
use Test::NoWarnings;

my @TESTS = (
  # dirty                               # clean
  [ q{The 99th bottle's x-o-x labels'} => q{The 99th bottle's labels'}
+ ],
  ...
  );

VECTOR:
for my $ar_vector (@TESTS) {

  if (not ref $ar_vector) {
    note $ar_vector;
    next VECTOR;
    }

  my ($dirty, $expected) = @$ar_vector;

  my $clean = clean_it_up($dirty);
  ok $clean eq $expected, qq{'$dirty' -> '$clean'};
  
  }  # end for VECTOR

done_testing;

exit;

# subroutine(s) ##############################

sub clean_it_up { ... }

...
[download]

See Test::More and friends.

Update: Changed to using q{...} in example code test sentences (was '...') because it's more compatible with embedded single-quotes. (Also a trivial wording change.)