If the line 89 is the code you past now, then the undefined value you're calling enquire_link_resp is $me in your 0x0...015 reply sub.
I presume that the call to that sub is not being done with the correct values. It looks like you have a complex code, so you may need to debug it carefully to find in which step you lose the $me value.
I had been working on perl smpp for last 1 week now.
Could you pls provide me the sample request and response smpp client. e.g. which sends bind request and then analyzes the bind response pdu.
Thanks a lot,