I tried this:

153 foreach (@str_handles) {
154   my $pid = $pm->start and next;
155
156   $b = syswrite $_->{handle},
157            join(" ",
158                   $_->{chunksize},
159                   $_->{A_cols},
160                   @A_lines[$_->{start}.. $_->{end}],
161                   @B_lines,
162                   "\cN"
163                );
164   # Wait until the writing has finished
165   #sleep(1);
166   $pm->finish;
167 }
168 $pm->wait_all_children;
[download]

But the behavior is the same.

Only the sleep seems to work.

My guess is that

$pm->finish;
[download]

produces a "fake termination": the local process ends while the remote is still writing?