$p="horraen=sumsel\[13\]\)\n";
 $m="sumsel\[13\]";

##</code><code>##

 $p="horraen=sumsel[13])\n";
 $m="sumsel[13]";

##</code><code>##

 $p="horraen=sumsel\\[13\\]\\)\n";
 $m="sumsel\\[13\\]";

##</code><code>##

 $p='horraen=sumsel\[13\]\)' . "\n";
 $m='sumsel\[13\]';

##</code><code>##

 $p="horraen=sumsel[13])\n";
 $m=qr/sumsel\[13\]/;