I have a code: 
#!/usr/bin/perl

use utf8;
use warnings;
use strict;

my $var1;
my $var2 = "0";
my $var3 = 0;
my $var4 = "a";

print isDef($var1)."\n";
print isDef($var2)."\n";
print isDef($var3)."\n";
print isDef($var4)."\n";

sub isDef {
  if (shift) {
    return "true";
  } else {
    return "false";
  }
}

[download]

The result of execution is: 

./test.pl 
false
false
false
true

[download]

The first variable is really undefined, but why second & third is undefined too?

p.s. Perl v5.14.1 built for i386-freebsd-thread-multi-64int

In reply to Validation: is defined whether the variable? by breeze

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