In my project I put assertion using regex in one of the step. It finds the message in the response and the regex gives me the other attribute values. But this works in ReadyAPI and not in SOAPUI free version.
Following is the regex which i was verifying:
CheckResult.CheckResultItem[?(@.MessageText=='A US 135 Outbound is required for this Leg and Customs is not available at KCMH')].CheckStatus
I am verifying the CheckStatus as [FAILURE]. But when I test the assertion it gives me 
I have attached the response. if you refer the CheckResultItem 6th index, I am trying to get the CheckStatus and Name values where I see the messagetext as 'Outbound Customs is required for this Leg and Customs is not available at VABB.'