And you beat me to whipping up a solution, though plugging your regex into my test proves that your regex works for the test cases I was able to think up:

#!/usr/bin/perl 

use strict;
use warnings;

my @input = ( "cocks are roosters!",
              "my cocks crow at dawn",
              "i'm a fan of the cocks",
              "game cocks all the way!",
              "do you like the gamecocks?" );
my $vulgar_list = {
                    cocks => { regex =>
                               qr/(?<!a)(?<!the)(?<!game)(?<!\s)\s*coc
+k/ }
                  };
my $foundvulgar;
for my $input( @input ){
  study($input);
  foreach my $word (keys %$vulgar_list) {
      my $regex = $vulgar_list->{$word}->{regex};
      if ($input =~ m/$regex/) {
          $foundvulgar = $word;
          last;
      }
  }
  print "phrase: $input found?: $foundvulgar\n";
  $foundvulgar = '';
}

__OUPUT__
phrase: cocks are roosters! found?: cocks
phrase: my cocks crow at dawn found?: cocks
phrase: i'm a fan of the cocks found?: 
phrase: game cocks all the way! found?: 
phrase: do you like the gamecocks? found?:
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s**lil*;  $*=join'',sort split q**;  s;.*;grr; &&s+(.(.)).+$2$1+; $; =
qq-$_-;s,.*,ahc,;$,.=chop for split q,,,reverse;print for($,,$;,$*,$/)
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