This works fine:

# 'main script'
require 'foo.pl';
foo();

# this is the content of foo.pl
sub foo{ print"foo" }
1;
[download]

Perl will look for 'foo.pl' in @INC which will usually contain these three directories:

/Perl/lib 
/Perl/site/lib
.

The . dir is the current dir. For more details on @INC see Simple Module Tutorial by tachyon Error messages are always useful when thing don't work. see also New Monks and the link on asking questions

doc

print(s<>ecode?scalar reverse :p)