chomp for @blocked; # don't expect to match newlines
if ( grep { $FORM{'comments'} =~ /\b$_\b/ } @blocked) {
  ...
}

[download]
This is somewhat simplistic, not to mention inefficient - the grep continues over every word in the list even if the first word matches. A better approach would use a for loop: 
chomp for @blocked;
for my $m (@blocked) {
  if ($FORM{'comments'} =~ /\b$m\b/) {
    # print your message here.
    exit;  #  could also last outside the loop
  }
}

[download]
The \b markers are to match at a word boundary, so BLOCK will not be matched in THIS SHOULD BE UNBLOCKED, for example.

However you may want to re-think your approach. Simplistic blockers like this rarely achieve the desired results, and often produce too high a level of false positives to be truly useful. YMMV, of course.

In reply to Re: Blocking based on words in a list by moot
in thread Blocking based on words in a list by matts156

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