$ cat My.pm
package My; our $VERSION = "1";
warn "1 loaded";
1;

$ cat 0/My.pm
package My; our $VERSION = "2";
warn "2 loaded";
1;

$ perl -I. -I0 -e 'use My 1; warn $My::VERSION;'
1 loaded at My.pm line 2.
1 at -e line 1.
$ perl -I0 -I. -e 'use My 1; warn $My::VERSION;'
2 loaded at 0/My.pm line 2.
2 at -e line 1.
$ perl -I. -I0 -e 'use My 2; warn $My::VERSION;'
1 loaded at My.pm line 2.
My version 2 required--this is only version 1 at -e line 1.
BEGIN failed--compilation aborted at -e line 1.
$?=255
$ perl -I0 -I. -e 'use My 2; warn $My::VERSION;'
2 loaded at 0/My.pm line 2.
2 at -e line 1.
$ perl -I0 -I. -e 'use My 1; warn $My::VERSION;'
2 loaded at 0/My.pm line 2.
2 at -e line 1.