$$text_ref =~ s|(?<="http://)(.*?)(?=["/])|$fixers{$1} ? $fixers{$1} : $1|ge ;

##</code><code>##

  my $what = join('|', map(quotemeta, keys %fixers)) ;
  $$text_ref =~ s!(?<="http://)($what)(?=["/])!$fixers{$1}!ge ;