$0 not supported (probably $N)

[v-python]

I just dropped the following into the tester, and it failed, saying $0 is not a valid string. But $0 is defined as the match string from the corresponding RewriteRule.

RewriteCond $0 !^cgi-bin/.[.]cgi
RewriteRule ^(.*)$ /cgi-bin/0.cgi/$1 [QSA,L]

The intent of these rules is to prefix the path of the url with a reference to a cgi file, but only if it doesn't already have it. They are broken, and I'm trying to figure out why/how, and found your tester.