PEP-292 introduced a nice Python templating feature.
Templates placehoder names are subject to some restrictions,Documentation says:

$identifier names a substitution placeholder matching a mapping key of "identifier".
By default, "identifier" must spell a Python identifier.
The first non-identifier character after the $ character terminates this placeholder specification.

This means that ...

Pdmenu is a menu system for Unix. It is designed to be easy to use, and is suitable for a login shell for inexperienced users, or it can just be run at the command line as a handy menu program.

I just modified showdir.pl script in order to implement ...