gjb is absolutely right, but let's go a little bit deeper.

undef == undef, I don't know whether you feel bothered by this fact of Perl.

  1. From a pure "correctness" point of view, I actually feel bothered. There is something in your left hand, and you don't know what it is. There is also something in your right hand, again you don't know what it is. Can you say that you have the same things in both of your hands? You cannot.
  2. Try these two pieces of code: 
    if ($a == $b) {
print "equals\n";
}

    [download]
    if ($a eq $b) {
print "equals\n";
}

    [download]
    Both pieces of code print out "equals", but at the same time, both complains that $a and $b are uninitialized. So we DOES observed some inconsistency.

When you use this undef value in a number context, perl evaulates undef to 0, and in a string context, evaluates undef to "" (empty string).

When you say undef == undef, both undef's are 0's, so 0 == 0. When you say undef eq undef, both undef's are "", so "" eq "".

In reply to Re: cgi problem by pg
in thread cgi problem by atnonis

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