invalid ban url syntax

[AD]

hello, when trying to ban a req.url from the CLI i get the following error,
any ideas?

ban req.http.host == "www.domain.com" && req.url ~ "\.png"
100 85
Unknown request.
Type 'help' for more info.
Syntax Error: Invalid backslash sequence

Removing backslash

ban req.http.host == "www.domain.com && req.url ~ ".png"
106 25
Wrong number of arguments

Cheers.
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