The tests

is( $ref->("hello.world.txt"), "helloworld.txt", "$f - simple" );           # 1
is( $ref->("hello-there"),     "hello-there",    "$f - zero periods" );     # 2
is( $ref->("hello..too.pl"),   "hellotoo.pl",    "$f - double" );           # 3
is( $ref->("magna..carta"),    "magna.carta",    "$f - double at end" );    # 4
is( $ref->("the-more-the-merrier.jpg"),
    "the-more-the-merrier.jpg",
    "$f - one period" );                                                    # 5
is( $ref->("hello."),    "hello.",   "$f - one period at end" );            # 6
is( $ref->("perl.txt."), "perltxt.", "$f - period at end" );                # 7
is( $ref->(".yes"),      ".yes",     "$f - one period at start" );          # 8
is( $ref->(".yes.txt"),  "yes.txt",  "$f - period at start" );              # 9