I used to be able to see essentially this page by typing, at the bash prompt, something like 'man perlvar'.

Works for me:

$ man perlvar | head
PERLVAR(1)             Perl Programmers Reference Guide             PE
+RLVAR(1)

NAME
       perlvar - Perl predefined variables

DESCRIPTION
   The Syntax of Variable Names
       Variable names in Perl can have several formats.  Usually, they
+ must
       begin with a letter or underscore, in which case they can be
       arbitrarily long (up to an internal limit of 251 characters) an
+d may
$
[download]

I suspect that you have installed some subset of perl using your OS package manager. Please refer to your OS instructions for how to install the full perl distribution, including the docs.