http://www.perlmonks.org?node_id=11126929


in reply to Re^5: hex numbers
in thread hex numbers

And of course code which assumes that the string can only ever contain hex digits is an exploit waiting to happen.

Code which doesn't assume the type of content of a variable but contains a string constant is only exploitable by editing the source file and munging the constant.

See my answer to davido below.

perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'