Using Perl 5.26.1 under Linux I want to use a variable in the searchlist of a tr operator expression. The example on p.76 of the camel book, has two things wrong with it

a) eval " ... code ... " as shown in the book gives an eval error message. To get rid of the message I need to put the code in braces.

b) even putting the code in braces it does not work. See this:

    $kards = -99;
    $bad="AKQJT98765432KKKK";
    $card='K';
    eval {print "eval is testing for $card in $bad \n"; 
           $kards = $bad =~ tr/$card//; # tried also tr/$card/$card/; 
+same bad result.
          };
    print "Num of $card in $bad = $kards \n";
    $king = $bad =~ tr/K//;
    print "Num of K in $bad is = $king \n";
=cut    
    Returns the following:
eval is testing for K in AKQJT98765432KKKK 
Num of K in AKQJT98765432KKKK = 0 
Num of K in AKQJT98765432KKKK is = 5 
=end
[download]

Why isn't the variable $kards set to 5 as it should be?

UPDATE

The problem is that $kards should be set to the result of the eval execution, not put inside the eval execution. So this works:

    $kards = -99;
    $bad="AKQJT98765432KKKK";
    $card='K';
    # this next bit works. xtr is just so I can print what eval is eva
+l ing.
    $xtr = "$bad =~ tr/$card//;" ;
    $kards = eval "$bad =~ tr/$card//;";    #<====== Note the ; " ; at
+ the end. This seems required.
        print "xtr kards = $kards from eval cmd : $xtr\n";
    #output: xtr kards = 5 from eval cmd : AKQJT98765432KKKK =~ tr/K//
+;
[download]

but note that the code eval runs must be in double quotes, not in braces. so <code>$kards = eval {$xtr;} ; does NOT work.