Select Code to Download

my %langTags=(
    perl => {
        HEAD => [
...
    },
    # ...
);

my %extToLang=(
    pl => 'perl',
    pm => 'perl',
...
    $lang=$extToLang{$1};
}
$lang or die "Missing language parameter";

use List::MoreUtils qw ( uniq );
my @allTags=uniq map { keys %$_ } values %langTags;