ruby: check if two variables are the same instance

According to the source, the Object#equal? method should do what you're trying to do:

// From object.c
rb_obj_equal(VALUE obj1, VALUE obj2)
{
    if (obj1 == obj2) return Qtrue;
    return Qfalse;
}

So the ruby code you would write is:

obj1.equal?(obj2)