What you're trying to do is use a "symbolic reference". Searching on that term will probably help a lot.

I see two problems here:

  1. First, use strict will prevent you from using symbolic references at all, because they are generally a bad idea. You should probably do as toolic suggested, and use a hash of hashes. That said, to turn off strictness, use no strict 'refs'; within a block.
  2. Second, symbolic references work by looking up the name of a variable in the symbol table. Only global variables live in the symbol table (though many are placed in packages); the other major type of variable in perl is a lexical variable, which does not appear in teh symbol table. You declare lexical variables using teh keyword my. By saying my %cs101 = ..., you've made it a lexical variable, gaurenteeing it will never show up in the symbol table, and a symbolic ref to it will not work. One way to declare global variables is to use the keyword our (this has aliasing affects in a package as well, but that won't affect things here.)
Here's a working version: 
use strict;
use warnings;

our %cs101 = ("joe"=>    "80" );

print "Choose which hash\n";
chomp (my $input = <STDIN>);
#my $whichhash=\%cs101;
my $whichhash="$input";

sub hashvalues {
   no strict 'refs';
   while( my ($key, $value) = each (%{$whichhash}) ) {
       print "$key $value\n";
   }
}

&hashvalues;

[download]
Read perldoc perlref, focusing on the sections for symbolic references.

--Clinton

In reply to Re: Dereference array via STDIN by clwolfe
in thread Dereference array via STDIN by gctaylor1

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.