subset Email of Pair where .key ~~ 'email' && .value ~~ /'@'/; subset AccountID of Pair where .key ~~ 'accountid' && .value ~~ Int && .value.chars ~~ 12; subset ID of Any where Email|AccountID; multi sub foo(Str $email --> ID) { email => $email }; multi sub foo(Int $accountid --> ID) { accountid => $accountid }; my $id1 = foo('p@p6.org'); say "id1 is Email? {$id1 ~~ Email}"; say "id1 is AccountID? {$id1 ~~ AccountID}"; my $id2 = foo(123123123123); say "id2 is Email? {$id2 ~~ Email}"; say "id2 is AccountID? {$id2 ~~ AccountID}";