Yes, this is true, but only for systems on which Perl is properly installed. It is probably installed correctly on modern Mac OS, *BSD and Linux-based systems, but on other Unixes, VMS and Windows it is sometimes installed badly. There still are sysadmins who only put perl.exe somewhere on the machine and think that it's enough. Then, of course, you don't get the documentation and you don't get the essential standard library modules such as File::Basename and Data::Dumper.
On systems that do have Perl properly installed you have all the perl* man pages and other monks already explained how to see their list.
I can add that in addition to to the perl* man pages such as perlfunc, perlop, perlre etc., you can also use perldoc to read documentation for any library modules that you have, from the standard library and from CPAN. Try: