package Planet; use Class::Struct mass => '$', radius => '$'; use Math::Trig; sub density { my $self = shift; my $vol = 4/3*pi*($self->radius)**3); return $vol/($self->mass); } package main; use Planet; my $Jupiter = Planet->new(mass => 1.8E27, radius => 6.9E7); print "Jupiter has mass of " . $Jupiter->mass . " and "; print "radius of " . $Jupiter->radius . "\n"; print "It's density is " . $Jupiter->density . "\n";