use B;

$foo = qr/foo/;
if ($foo->isa("Regexp")) {#check whether it is a Regexp object
	print "is a Regexp\n";
} else {
	print "is not a Regexp\n";
}

print B::svref_2object($foo)->MAGIC->TYPE;#if it is not a sv ref, perl will not allow you to call svref_2object