use Getopt::Long;
my %OPT;
GetOptions \%OPT, qw/ help|h DEBUG / or ($OPT{help} = 1);
if ($OPT{DEBUG}) {
    # whatever you like:
    require Data::Dump;
    eval "use Carp::Always";
}

...

say "Got some data:\n", Data::Dump::pp(\%my_data) if $OPT{DEBUG};