Can i use regular expressions while creating aep audience through segmentataion service?

Hi ,  as part of the requirement i need to check for a specific pattern of consent where i have to use regex in audience. as far as i know there is no way that i can use regular expression in audience. So, i am trying to use segmentation service where i need to use pql to achieve the same. but i am getting “ 403 Forbidden User region is missing “  error. 

Can anyone please let me know if it’s possible through segmentation api’s or can let me know why i am getting region mission error. i am giving below headers in the request.

1.Accept

2.Content-Type

3.Authorization

4.x-api-key

5.x-gw-ims-org-id

6.x-sandbox-name

7.x-request-id

Thanks in advance.

Usha.