Actually, you can require them. However, if there is any code inside that isn't wrapped in a sub, it will execute when the file is required. Example:

#!/usr/bin/perl
### the file doing the requiring

use strict;
use warnings;

use lib '/path/to/lib';
require('tmp.pl');

asdf();
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---

#!/usr/bin/perl
### the file being required

use strict;
use warnings;

print "hi there\n";

sub asdf { print "well howdy"; }

1;
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---

### the output
hi there
well howdy
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