Thank you to all your suggestions. So I tried to modify my example program in two ways:

• Make output unbuffered in both programs
• Make sure that Control-Z is sent on Windows before the output handle is closed.

This results in the following programs:

# This is cat.pl
$|=1;
while(<>) {
  print;
}
chr(0x1a) if $^O eq 'MSWin32';
[download]

and

# This is ls.pl
use strict;
use warnings;
use IPC::Open2;
# OUTPUT: Filehandle for output from cat.pl
# INPUT: Filehandle for input to cat.pl
open2(*OUTPUT,*INPUT,"$^X", "cat.pl") or die "$!";
print INPUT "first line\nsecond line\n";
if ($^O eq 'MSWin32') {
  select INPUT;
  $| = 1;
  print INPUT chr(0x1a);
}
close INPUT;
my @result=<OUTPUT>;
close OUTPUT;
print "RESULT:\n@result\n";
[download]

Still, using the programs on Windows like this:

perl ls.pl
[download]

causes it to hang.

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