Raku Books / Perl 6 at a Glance / Code Organization / Subroutines, or subs
Optional parameters
Optional parameters are marked with a question mark after their
names. The defined built-in function helps to tell if the
parameter was really passed:
sub send-mail(Str $to, Str $bcc?) {
if defined $bcc {
# . . .
say "Sent to $to with a bcc to $bcc.";
}
else {
# . . .
say "Sent to $to.";
}
}
send-mail('mail@example.com');
send-mail('mail@example.com', 'copy@example.com');