That's why the distribution includes documentation. And why learning to use (in this case) perldoc cgi (or, on a case-sensitive system, *nix among others, perldoc CGI) at your command prompt is worth doing.

That's the syntax for a module you have installed; perldoc -f function name will also be useful time after time, and if you have a real interest in the breadth of built-in documentation, try perldoc perldoc.

Update: Thanx to choroba for calling my attention to the need, for some users, to "s/cgi/CGI/"