~/a.pl:
---8<--
#!/usr/bin/perl
# vi:ts=4 sw=4 et:
use strict;
use warnings;
use lib '/tmp';
use bar::foo;

bar::foo->hello();
__END__
---8<--

/tmp/foo/bar.pm:
---8<--
package foo::bar;

sub world {
	return "world!";
}

1;
__END__
---8<--


/tmp/bar/foo.pm:
---8<--
package bar::foo;
use foo::bar;

sub hello {
	print "hello ", foo::bar::world(), $/;
}

1;
__END__
---8<--

~$ perl ~/a.pl 
hello world!
~$