YAATIUOWBWOL - Yet another attempt that is untested on windows but works on linux.

#!/usr/bin/perl

use strict; # https://www.perlmonks.org/?node_id=11154445
use warnings;

use IO::Socket;
use IO::Select;

my $port = 3333; # FIXME
my $childstayup = '/tmp/childstayup'; # FIXME
open my $fh, '>', $childstayup or die $!;
close $fh;
my $listen = IO::Socket::INET->new( LocalPort => $port,
  Listen => 100, ReusePort => 1,) or die $&;

if( my $pid = fork ) # parent
  {
  print "Hit <ENTER> to quit\n";
  <STDIN>;
  unlink $childstayup;
  1 while wait > 0;
  print "parent exiting\n";
  }
elsif( defined $pid ) # child
  {
  my $sel = IO::Select->new( $listen );
  while( -e $childstayup )
    {
    for ( $sel->can_read( 1 ) )
      {
      if( my $live_socket = $listen->accept )
        {
        my $input = '';
        while( <$live_socket> )
          {
          $input .= $_;
          /^\r?\n?\z/ and shutdown($live_socket, 1), last;
          }
        print "process 'do stuff' here with:\n$input";
        }
      }
    }
  print "child exiting\n";
  exit;
  }
else # bummer
  {
  die "fork failed $!";
  }
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Sort of a combination of mine and yours...

UPDATE: fixed 'for' variable name