#here
while (<IN>) {
#for (<IN>) {
 chomp;

 $rcount++;
 $tcount++;
 print "Progress: $tcount\n";   # changed \r to \n
 $pid = fork;

 if ($pid==0) {
 # child
  close IN;
  print "child pid $$\n";       # new debug line
  # start call sleep sub
[download]

your script produces

Progress: 1
child pid 21079
Progress: 2
child pid 21080
Progress: 3
child pid 21081
Progress: 4
child pid 21082
...
[download]

so I guess it works as expected. It is definitely a better to use while() if you don't need the entire bunch of lines (e.g. to sort them first), but one line at a time.

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}