    #!/usr/local/bin/perl -w

    use File::Basename;
    use Getopt::Long;

    my $ret = GetOptions ("f|filename:s");
    my $filename = $opt_f || die "Usage: $0 -f filename\n";

    # Return the dirname of the given filename.
    my $dirname = dirname($filename);
    print "The directory name of $filename is $dirname\n";