If you're certain that the file names are always as simple as you described (one dot per name), then you can use fileparse without an extension arg; this leaves the extension attached in the return value, which you can then split on period:

use File::Basename;

for ( qw{foo/bar.ext ../moo/mar.ble} ) {
    my ( $name, $ext ) = split( /\./, fileparse( $_ ));
    print "$_ => $name and $ext\n";
}
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