our $earth_revolution = 31557600;

our %planets = (
    mercury => 0.2408467,
    venus   => 0.61519726,
    mars    => 1.8808158,
    jupiter => 11.862615,
    saturn  => 29.447498,
    uranus  => 84.016846,
    neptune => 164.79132,
    earth   => 1,
);

sub age-on( $planet, $seconds ) is export {
    ( $seconds / %planets{$planet.lc} / $earth_revolution ).round(0.01);
}