Perl searches the module in the current directory, not the directory where the srcipt resides. Make sure to cd to the directory, and call perl mod.pl from there. The module and the code you've included work for me, except for that test_print does not print a newline. If, by any chance you have a \r in your shell prompt (assuming you're not on windows; yes, I was so stupid once to put a \r in my prompt), you won't see the output.