User Variable Condition

You can check whether the user variable has been already assigned a value. The syntax of the condition is:

User Variable [variable name] is set / is not set

where [variable name] is the name of the variable that you are checking.

Until you set a variable's value, either using "View Variables" or through a trigger's "set user variable" action, it is considered to be "not set".

As soon as any value is assigned to this variable (even if it is a zero), it is reckoned to be "set".

If a variable is not set, it is not parsed if met in trigger expressions. Its name is not replaced with any value until it gets "set". You should take this into account when creating your triggers.