$null
From Scriptwiki
Returns absolutely nothing. Used to compare values in If-Then-Else checks.
$null
- This identifier has no options or parameters.
Example
The first example shows the common use, if any, of $null.
if (%age == $null) { echo -a the variable does not exist } elseif (%age != $null) { echo -a the variable does exist! }
The same thing can be done with simple checking, as shown below.
if (!%age) { echo -a the variable does not exist as it returns nothing when called } else { echo -a it does not not exist, hence it must exist, woho. }