sub gen_reduce {
    my $usage = 'Usage: gen_reduce("initial" => $val, "compare" => $code_ref)';

    # Hashes need even number of arguments
    die $usage if @_ % 2;
    my %opt = @_;

    # Verify that compare defined and a code reference
    die $usage if ! defined $opt{compare} || ref $opt{compare} ne 'CODE';
    my $compare = $opt{compare};
    my $val = $opt{initial};
    # FINALLY start the actual function