We apologies for the delay. We support Regex in the HTTP Response Header(s) check. This lets you add the desired response Header-Value for your HTTP request and we'll verify if the values match your regex. If the check fails, an alert will be triggered.
Here is the help document which details more about this feature.
You can add HTTP Response Header(s) check by navigating Web > Website and then click on the hamburger icon on the far right corner of the selected monitor then choose Edit.
You can see it under "Content Checks" section with the label "Should contain HTTP Response Header(s)".
Please refer the below screenshot for your reference.
We hope this meets your requirement and let us know if you have any further queries.
Product Developer, Site24x7