One of the perl command line flags is "-P" which instructs perl to run the C preprocessor upon the source of the script.

 So "test.pl":

print "Before\n";
#include "test2.pl"
print "After\n";
[download]

 And test2.pl:

print "During\n";
[download]

 Will do the right thing if you run "perl -P test.pl" - producing:

Before
During
After

 However I suspect this isn'te really what you want to do - and the replies mentioning modules are the real solution to your problem.

 (OT: Using ActivePerl 'perl -P' crashes immediately under Windows, and has as long as I can remember. Weird.)