my $string = '<a href=\'http://www.perlmonks.org/?node_id=646560">here
+</a>';
$string =~ s{<a href=(?:\"|\')*(?:\w+\://)*(?:www.)*perlmonks\.org/\?n
+ode_id=(\d+)(?:\"|\')*>([a-zA-Z\d\s\:\.\/\_\-]+)</a>}{[id://$1|$2]}gs
+;
[download]