I want to have such pipe in bash

#! /usr/bin/bash
cut -f1,2 file1.txt | myperl.pl foo | sort -u 

Now in myperl.pl it has content like this

my $argv = $ARG[0] || "foo";

while (<>) {
 chomp;
 if ($argv eq "foo") {
  # do something with $_
 }
 else {
   # do another
 }
}

But why the Perl script can't recognize the parameter passed through bash? Namely the code break with this message:

Can't open foo: No such file or directory at myperl.pl line 15.

What the right way to do it so that my Perl script can receive standard input and parameter at the same time?