Is it possible use or require a Perl script without executing its statements?

Question

I need to add unit testing to some old scripts, the scripts are all basically in the following form:

#!/usr/bin/perl

# Main code
foo();
bar();

# subs
sub foo {         


        

Answer 1

Ahh, the old "how do I unit test a program" question. The simplest trick is to put this in your program before it starts doing things:

return 1 unless $0 eq __FILE__;

__FILE__ is the current source file. $0 is the name of the program being run. If they are the same, your code is being executed as a program. If they're different, it's being loaded as a library.

That's enough to let you start unit testing the subroutines inside your program.

require "some/program";
...and test...

Next step is to move all the code outside a subroutine into main, then you can do this:

main() if $0 eq __FILE__;

and now you can test main() just like any other subroutine.

Once that's done you can start contemplating moving the program's subroutines out into their own real libraries.