#!/usr/bin/perl -w
use IO::Socket::UNIX;
use strict;
my $sockfile = '/tmp/mysocket';
my $r;
unlink($sockfile);
my $usock = new IO::Socket::UNIX(
   Type => SOCK_STREAM, 
   Local => $sockfile, 
   Listen => 1) 
  || die "ERROR: $!\n"; 

while (1) {
  if (($r) = $usock->accept) {
    my $out = do_something($r);
    $r->printflush($out);
    # sleep 1; # this makes it work
    $r->close;
  }
}

sub do_something {
  my ($fh) = @_; 
  my ($l) = <$fh>;
  return uc($l);
}