my $message = join '', map cleanline($_), <DATA>;
  ...
  {
    my $prevline;
    sub cleanline {
      my $line = shift;
      # skip duplicate lines
      return if defined($prevline) && $line eq $prevline;
      $prevline = $line;
      # crudely HTMLify
      return "$line\n<br>\n";
    }
  }

##</code><code>##

   if ($biglist =~ m%$bq%ig )        # 
      {
       $biglist =~ s%$bq% %ig;         # replace with space, case insensitive, g
lobal
      }

##</code><code>##

  $biglist =~ s%$bq% %ig;

##</code><code>##

<pre>
blah blah blah blah blah

Andrew Darby
Web Services Librarian
Ithaca College Library
<a  rel="nofollow" href="http://www.ithaca.edu/library/">http://www.ithaca.edu/l
ibrary/</a>



Vishwam Annam wrote:
</pre>

##</code><code>##

  our $re_bq;
  $re_bq = qr{
    # open tag
    < blockquote
      (?: \s+ style \s* = \s* " .*? " )? \s*
    \s* >
    (?:
      # some character that doesn't start a nested blockquote
      (?!<blockquote\b) .
    |
      # or a whole (recursively) nested blockquote
       (??{ $re_bq })
    )*
    < / blockquote \s* >
  }xsi;
  ...
  $message =~ s{$re_bq\s*\z}{};