CGI and Perl actually are the same, CGI is considered a language by the Unix community at least and since they are the ones who made it, i'd go with them. PHP is actually the easiest by judgment, since it automatically decides if something is a string, int, etc. CGI is just a different version of perl. and is indeed a different language. The reason i say that PHP is easier is because i learned php in 10 mins while Perl took 45.
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AH if you know PHP you are well on your way to GScript, there are many differences but if you can learn PHP you can DEFINATLY learn GScript. There are array() = setarray, messages = echo, etc. So just do as Kaimetsu says and all will be good, cause kaimetsu is the intellegence of the forums, we are all his drones.