You might want to put $|++ in your main script to avoid buffering output, but with the \n in there, it should print anyways.

I think your problem is your "read STDIN, $stuff,10" statement. It will wait for 10 chars, try "read STDIN,$stuff, 1". That works on linux.

If you want readline on the stdin, try this

#!/usr/bin/perl
use FileHandle;
use threads;

$|++;

$thr = threads->new(\&sub1);

sub sub1 {
  while(1){
  print "THREAD: in da zone !! :) \n\n";
  sleep 1;
  };
}

my $fh_in = FileHandle->new();
$fh_in = *STDIN{IO};                                                  
+                 

while (<$fh_in>) {                                                    
+                    
    my $stuff = $_;
    if (defined($stuff) and $stuff ne ''){
      print "MAIN:", $stuff , "\n" ;
    }
 }
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