As far as name clashes go: you're explicitly asking for one command, so thats probably the one you want to use

Very good. Obviously I don't know enough about Shell.pm, so disregard my comment ;-)

I would also tend to question the sanity of a system that had programs with such similar names yet differing functionality.

Me too, but as a module author you're in no position to judge your user's sanity, or the sanity of their systems.

I hadn't thought of '+', because it hadn't come up for me yet. Thanks.

If you want to do it properly, either look into the source code of a POSIX compatible shell or in the POSIX standard itself to get a list of all characters that can be used in commands without the need for escaping. On thinking a bit more I remember that there's /usr/bin[ on my system (for stuff like if [ .. ], so there could well be many other allowed characters.

Maybe just substitute anything but [a-zA-Z0-9_] with underscores?