What you're interested in is command line processing -- notice the '-e' switch all the users here supplied to the perl command. think of it as 'execute'.

You'll find the information you need in perldoc perlrun in the Command Switches section.

A bit of document searching that is often suggested here, and I've found quite useful is 'perldoc -q FAQRegex' -- where FAQRegex is, a, well, regex.