At the point where this statement executes, with $/ having any sort of string value (including the default line terminator):

while (<SOCKETHANDLE>) {
  ...
[download]

I think the potential damage will already be done, if the process at the other end of the socket happens to write, say, 4 GB of data with nothing that matches $/.

(Then again, I could be wrong about that, 'cuz I haven't tested it... does the <> mechanism provide some sort of safe buffering or allocation method to avoid stuffing an impossible amount of data into $_? If so, this seems magical and quite unexpected.)