It isn't really that important.  Use what you're comfortable with,
or what you're constrained (eg by your manager) to use.

If you're just dabbling with programming, Perl is a good choice, simply
because of the wealth of ready-to-run Perl/CGI resources available.

If you're serious about programming, you should be at home in a
range of languages.  C, the industry standard, is a must (at least to
the level of comfortably reading other people's code).  You'll
certainly want at least one scripting language such as Perl, Python
or Tcl.  C++ is also a good idea.

In response to a Usenet newbie question:
>  I am seriously wanting to learn some CGI programming languages

J.M. Ivler wrote some eloquent words of wisdom:
> If you want to learn a programming language, learn a programming language.
> If you want to learn how to do CGI programming, learn a programming
> language first.
> 
> My book is one of the few that tackles two languages at the same time.
> Why? because it's not about languages (which are just syntax for logic).
> CGI programming is about programming, and how to leverage the experience
> for the person coming to the site, or maintaining the site, or in some way
> meeting some requirements. Language is just a tool to do so.