my $buffer;

while (my $line = $socket->getline())
{
     # Maybe this is the "END" line, and if it is,
     # bail out of the loop because we're done!
     last if ($line =~ /^END$/);

     # Otherwise, just tack that stuff onto the buffer.
     $buffer .= $line;
}

print "Read: ", $buffer, "\n";