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

my $mystring = "ABC<ID>blahblah</ID>DEF";
if ( $mystring =~ /<ID>($.)<\/ID>/) {
  my $ID = $1;
  print "$ID\n";
}

##</code><code>##

dpich@m6400-vb:~/Documents$ perl ./xml.pl
Use of uninitialized value $. in regexp compilation at ./xml.pl line 6.
dpich@m6400-vb:~/Documents$