if Flow control command
Usage
if (<condition>) <command1> [else <command2>]
Description

Executes <command1> if the <condition> evaluates to true (non zero result).
If the else part is given, <command2> is executed.
If the <condition> evaluates to false (result == '0').
the <condition> is an expression evaluated in the same way as $(*) with the following extensions:
If the <condition> is a string, its length is evaluated - in this way a non-empty string causes the <condition> to be true, and an empty string causes it to be false.
If the <condition> is an array, its size is evaluated - a non-empty array is true, an empty array is false.
If the <condition> is a hash, the number of its entries is evaluated - a non-empty hash is true, an empty hash is false.

Examples
if(%a != 10) echo \%a was != 10 else echo \%a was 10!
See also
Expression evaluation identifier

Index, Commands