# Pastebin 8b1t9ujH
method values-or-defaults(%hash, $key) {
    return %hash if not %hash;

    my %output = %hash<default>;

    if %hash{$key} -> %overrides {
        %output = |(%output), |(%overrides)
    }

    if not %output {
        # throw exception
    }
    return %output;
}