Question

I want my perl script to be able to do this:

$ ./code file.txt | myperl.pl param1 param2

So basically it will take input (STIDN) from ./code and execute it with param1 and param2.

But why this doesn’t work:

my $param1 = $ARGV[0];
my $param2 = $ARGV[1];

while (<>) {
   if ($param1 > 0.5 && $param2 > 0) {
     # do something
  }

}

What’s the right construct to do it?

Answer 1

<> aka readline‘s default argument is ARGV, which is a magic filehandle that reads from all the files specified in @ARGV, or from STDIN if there are none. Since you are providing arguments, you either need to clear them out of @ARGV before using <>, or explicitly specify <STDIN> and not use the magic ARGV handle.