use B;
use constant CONST => 0x0200;

sub is_constant {
    no strict 'refs';
    my $name = shift;
    my $code = *{$name}{CODE};
    my $obj = B::svref_2object($code);
    return 1 if $obj->isa('B::CV') and $obj->CvFLAGS & CONST;
    return 0;
}