my $debug = 0;
my $usage = "Usage: $0 [-d|-h] month start end\n blah blah";
if ( @ARGV and $ARGV[0] =~ /^-+([dh])/ ) {
    shift;
    die $usage if ( $1 eq 'h' );
    $debug++;
}
die $usage unless ( @ARGV == 3 ); # could add more conditions...