$ cat Foo/Mod.pm
package Mod;
$VERSION = 1;
1;

$ cat Bar/Mod.pm
package Mod;
$VERSION = 2;
1;

$ perl -e'use lib qw( Foo Bar ); use Mod 2;'
Mod version 2 required--this is only version 1 at -e line 1.
BEGIN failed--compilation aborted at -e line 1.