That looked totally wrong. (and your end-tags miss a / (/code instead of just code).

sub usage
{
    my $err = shift and select STDERR;
    print "usage: $0 ...\n";
    exit $err;
    } # usage

use Getopt::Long qw(:config bundling);
my $be_consistent = 0;
my $sum           = 0;
my $threshold     = 0.0;
my @junk_files;
GetOptions (
    "h|help"         => sub { usage (0) },
    "c|consistent!"  => \$be_consistent,
    "s|sum!"         => \$sum,
    "threshold:f"    => \$threshold,
    "junk_files=s"   => \@junk_files,
    ) or usage (1);
[download]

As suggested, you should read the manual.

As a side note, I have no idea what --no-help would do :)