gistfile1.txt

#!/usr/bin/env perl6

use v6;

class IssueProperty {
    multi method ACCEPTS($) {
        False
    }

    multi method ACCEPTS(Any:U $class: Str $) {
        True
    }
}

class IssueAssignee is IssueProperty {
}

sub MAIN(Str :$assignee where IssueAssignee) {
}