How to convert string variable to number?

Hi, Aaron,

 

From example below.

 

I try to mod string type($subid) by 4 but I'm not sure that what type will return?

 

 

set subid [findstr [HTTP::payload] "subscriberNumber" 0 ""]

 

set modid expr {$subid % 4}

 

 

 

Thank you,

 

Paritchaya