Howto filter https with squidguard regular expressions

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I've set up a Pfsense versions 2.3.4.1 with squid and squidguard.  Blocking HTTPS traffic by the URL list is no problem (I just add an '/' to a domain in the URL list). So I know squidguard is able to block HTTPS on my pfsense. However I just can't manage to filter HTTPS traffic by Regular Expressions. For example, when I want to block audi, i use .audi|.Audi|.audi.|.Audi. a bit primitive perhaps, but it works. What token should I use to block HTTPS? using the same '/' as in the URL list doesn't work. In advance thanks for any suggestions.