sub bar { 1 };
sub baz() { 1 };
*zip = sub{ 1 };
*zap = sub(){ 1 };

foreach ( qw/ FOO One::FOO Two::FOO bar baz zip zap / ) {
    if ( Two::is_constant( $_ ) ) {
        print "$_ Yes\n"; #$_ so i know which one i'm checking
    } else {
        print "$_ No\n";
    }
}