As other posters have pointed out, Perl isn't shell, although it can be used that way.

You make calls, via backticks (``) to external commands - even to call text processing tools such as awk, when you could do most of it internally with perl.

There are modules on CPAN that allow you to look at the process list on UNIX systems (see Proc::ProcessTable)

dragonchild has give you a good example - you should work through the way his example works and learn from it.

Cheers

BazB