How do I increase the verbosity level to find out what's going wrong here?

Item 1 in the Basic debugging checklist suggests to use warnings which you are not doing here. Enable that for starters.

$socket->recv( $ret,$maxlen ) or die "Fail: $!";

The docs for recv say:

Returns the address of the sender if SOCKET's protocol supports this; returns an empty string otherwise. If there's an error, returns the undefined value.

But your statement only tests for truth rather than definedness. Try this instead, perhaps:

$socket->recv( $ret,$maxlen ) // die "Fail: $!";