I'm trying to test for a parameter with shift or die.
The parameter in this case is zero, so I am wary of dodgy true/false interpretations on my part. However, with @_ being three items long, shift populates the variable it is supposed to and then dies as well.

Why?
Is it because shift is returning zero which is evaluating to false? I was expecting shift to return success if it could shift an item.
Is there an alternative operator I could use or some conbination of shift / defined? 

#!/usr/local/bin/perl -w
use strict;

lookup(22);
lookup(22, 'data');

my $var = 111;
lookup(22, 'data', $var);

$var = 0;
lookup(22, 'data', $var);
sub lookup {
    print "Num params", scalar (@_), "\n";

    my $self      = shift;
    my $data_type = shift or print "type not provided ConfReaderlookup
+\n";
    my $item      = shift or print "item not provided ConfReaderlookup
+\n";

    print "ITEM isnt in here actually\n" unless defined $item;
    print "----------------------------\n";
}

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In reply to shift, undef and 'or die' by agoth

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