You're getting confused between the key and the hash. The hash is a list of key value pairs, as you've saved. However, you access the values of %hash with the syntax $hash{$key}, so a working version of your code might look like:

%friends= ("Bill" => "313-333-5555",
           "Bob" => "313-777-98755",
           "Joe" => "313-555-4435",
          );
print "Which phone number do you want?\n";
$name = <STDIN>;
chomp $name; # To remove trailing newline
print $friends{$name};
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To learn more about accessing hashes, see Perl variable types in perlintro.