while  (my $token = $stream->get_token) {
  if (($token->[0] eq 'C' and 
       $token->[1] eq '<!-- InstanceBeginEditable name="article" -->')
      ..
       ($token->[0] eq 'C' and $token->[1] eq '<!-- InstanceEnd -->')){
    print $token->[1];
  }
}

##</code><code>##

my $parsing=undef;
while  (my $token = $stream->get_token) {
  if ($token->[0] eq 'C' and 
      $token->[1] eq '<!-- InstanceBeginEditable name="article" -->'){
    $parsing=1;
  } elsif ($token->[0] eq 'C' and 
           $token->[1] eq '<!-- InstanceEnd -->') {
    $parsing=undef;
  } elsif ($parsing) {
    print $token->[1];
  }
}