squid doesn't accept acl rule with NOT containing substring regex

I am using following rule to filter request header in squid.conf, the purpose is to match header value which does not contain string "abc"

acl noabc req_header X-My-Header ^((?!abc).)*$

But it gives error

FATAL: Bungled /etc/squid/squid.conf line 1594: ...

Solution

Thanks to Wiktor, lookaround is not supported

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