irule - check query parameter

Hi

I would like to check if specific query parameter (ids) in url is above some numeric value (300), if yes then redirect to specific page.

Sample https request: https://xyz.ab/some/path/additition?lang=en&ids=300

How to check if this parameter is only number and not string  ?

Sample irule

WHEN HTTP_REQUEST {

if {[HTTP::uri] starts with "/some/path" and [URI::query [HTTP::uri] ids ] > 300 }

{ HTTP::redirect "https://xyz.ab/404.html" }

}

When i add some string to ids for example ids=300ab above irule also redirects so  how to validate this query parameter so that if and only if it is a number and is above 300 it will redirect to specific page ?