#! /usr/bin/perl -w
  use strict;

  my $html = qq{
  blah
  <!-- comment -->
  blah
  <!--
   comment
  -->
  blah
  };

  print "m: $_\n" for $html =~ /(<!--.*?-->)/sg;

  my $r = qr/<!--.*?-->/;
  print "qr: $_\n" for $html =~ /($r)/sg;

  $r = qr/<!--.*?-->/s;
  print "qrs: $_\n" for $html =~ /($r)/g;