Hi @Jarosław Bortel ,
Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.
I understand that you are trying to use "Regex" under Rule Engine of classic AFD.
"Regex" and "NotRegex" operators are not supported under classic AFD Rules Engine.
To make use of the above, we would be required to upgrade to Standard/Premium AFD Plan.
I have created an internal work item to update the document and it should reflect soon.
Thanks,
Kapil
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