[test]$ cat test.pl 
#!/usr/bin/perl -w

use strict;

use dir::mod;

hello("world");
[test]$ cat dir/mod.pm 
package mod;

use strict;
use warnings;

use Exporter;
our @ISA = qw(Exporter);

our @EXPORT = qw(hello);

sub hello {
  print "hello " . shift() . "\n";
}

1;
[test]$ ./test.pl 
Undefined subroutine &main::hello called at ./test.pl line 7.
[test]$