my ($dir) = m{/([^/]+)/[^/]*$};

##</code><code>##

my ($dir) = m{
               /        # Preceeded by a slash.
               ([^/]+)  # Preceeded by non-slashes, the dir. Captured.
               /        # Preceeded by a slash.
               [^/]*    # Preceeded by non-slashes, the file name.
               $        # End of string.
            }x;