If you call the code below stdin.pl,

while(<>) {
    print;
}
[download]

then all three commands below result in the same output:

$ perl stdin.pl stdin.pl
$ perl stdin.pl < stdin.pl
$ cat stdin.pl | perl stdin.pl
[download]

you're right

from perlop

       The null filehandle <> is special: it can be used to emulate the
       behavior of sed and awk.  Input from <> comes either from standard
       input, or from each file listed on the command line.  Here’s how it
       works: the first time <> is evaluated, the @ARGV array is checked, and
       if it is empty, $ARGV[0] is set to "-", which when opened gives you
       standard input.  The @ARGV array is then processed as a list of
       filenames.  The loop


           while (<>) {
               ...                     # code for each line
           }


       is equivalent to the following Perl-like pseudo code:


           unshift(@ARGV, '-') unless @ARGV;
           while ($ARGV = shift) {
               open(ARGV, $ARGV);
               while (<ARGV>) {
                   ...         # code for each line
               }
           }

Cheers Rolf

( addicted to the Perl Programming Language)

OK ... sorry ... I never needed that magic ...

Your code is too long for me to spot the reason, you should try shortening it till you isolated the problem.

Maybe one of your modules (like IO::Select ) clutters something?

Cheers Rolf

( addicted to the Perl Programming Language)

I still do not know why your code does not work. I wanted to reply to LanX only. Apologies for cluttering your thread. I'll be silent now.