Well you have multiple options. First there is the possibility of forking. Secondly you can do a bunch of system commands with &s then proceed when wait says that they are done. Thirdly you can use asynchronous IO, which is basically having multiple handles open, then using select to read from them one at a time.

If you want to follow the latter approach there is a discussion of how to do it in raw code in perlipc. Life may become easier (at least once you've learned the library) if you use a library that is meant to support asynchronous IO. CPAN has many such libraries. Including POE, Event::Lib, and the new kid on the block, IO::Lambda. If you want to look at the last you probably want to look at the discussion about it at IO::Lambda: call for participation, and particularly my response at Re^2: regarding 1.02 (was Re: IO::Lambda: call for participation).