Hello Monks,

May be I am not phrasing this question properly. In a nutshell, I expect one argument to be pased to the script. However, I am doing the checking for it in a sub, which eventually receives this argument.

So, I blatently pass $ARGV[0] to the sub regardless of whether any arguement was passed to the script or not. I do the checking of # of arguments in the sub (May be not the right place to do so). I actually exected @_ to contain no entries. Yet, it contains 1. But the retrieved value using shift is undefined.

#! /usr/bin/perl
use strict;
use warnings;

sub p1 {
    my $n1;
    $n1=@_;
    print "1. Parameters to the sub p1 $n1\n";
    my $p1=shift;
    print "2. p1=$p1\n";
}
p1 $ARGV[0];

[download]
So, here is my academic curiosity question:

Arguments is Perl are passed by reference. Argument $ARGV[0] never existed in memory (If I did not pass anything argument to the script), so there is no address for it. So shouldn't @_ say 0? How else would you (recommend) check for passed arguments to be present if this does not work?

Thanks.

Ash

In reply to Question: Is undef a valid argument? by jujiro_eb

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