If you're using Perl from a command line, the blank screen is the Perl interpreter's console. If you type a Perl program into it and hit control-d (or whatever EOF is on your system) it will execute. You might find it easier to write programs as text files, however, and to run them using 'perl file.pl' (or your system's equivalent). This allows for easy manipulation of your code, and easier debugging.

As for running programs from Perl, there are a few ways to do it. The exec, system, and backticks (``) all work well. (Note: those links are for Perl 5.6. Documentation for other versions of Perl may be found on the same site).
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Love justice; desire mercy.