For all the firewalls Europe put in place over the last three years, the actions investors say they would take if Greece left the euro currency bloc suggest the ensuing panic would rumble through financial markets. The imminent launch of a bond-buying scheme from the European Central Bank has so far quelled the anxiety that in 2012, when Greece last looked set for the exit, prompted a steady stream of money out of the euro zone. Investors say the euro would take a hammering as foreign funds sought shelter in U.S.