(I do know about File::Tail, in case anyone was going to suggest that, but I couldn't see how to implement it non-blocking and integrate that with the socket listener.)

Actually, File::Tail has a select for that very purpose. The way to use it is to pass all the socket filehandles to File::Tail's select exactly the way you'd pass them to the regular select.

Then you take all the File::Tail objects, and you put them behind all the other parameters in the select. Select will return when any of the filehandles are ready for reading, and File::Tail's select will do exactly the same, except it will also return if any of the File::Tail objects have stuff to read.

foreach (@ARGV) {
    push(@files,File::Tail->new(name=>"$_",debug=>$debug));
}
while (1) {
  ($nfound,$timeleft,@pending)=
        File::Tail::select(undef,undef,undef,60,@files);
  foreach (@pending) {
    print $_->{"input"}." (".localtime(time).") ".$_->read;
  }
}
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So, to use File::Tail for this, just replace the undefs in the select call with the appropriate bit vectors for your socket filehandles.