use Switch;

    switch ($val) {
        case 1          { print "number 1" }
        case "a"        { print "string a" }
        case [1..10,42] { print "number in list" }
        case (@array)   { print "number in list" }
        case /\w+/      { print "pattern" }
        case qr/\w+/    { print "pattern" }
        case (%hash)    { print "entry in hash" }
        case (\%hash)   { print "entry in hash" }
        case (\&sub)    { print "arg to subroutine" }
        else            { print "previous case not true" }
    }

##</code><code>##

    syntax (switch (EXPR) CODE) { # eval the expr first to avoid
                                  # reevaluation at each case
      my $var = new_unique_symbol;
      code {
        {
          $var = EXPR;
          switch_aux($var) CODE  
        }
      }
    }
    syntax (switch_aux (EXPR) { case CODE_t { CODE_c } CODE_e }) {
      # else is left as an excercise.
      code{
        if(case(EXPR,CODE_t)){
          CODE_c
        } else {
          switch_aux(EXPR){ CODE_e } # notice the recursion here
        }
      }
    }
    syntax (case (EXPR,INTEGER)){
      code {
        (EXPR == INTEGER)
      }
    }
    syntax (case (EXPR,STRING)){
      code {
        (EXPR eq STRING)
      }
    }
    syntax (case (EXPR,LIST)){
      code {
        (grep EXPR, LIST)
      }
    }
    syntax (case (EXPR,REGEX)){
      code {
        (EXPR =~ REGEX )
      }
    }
    syntax (case (EXPR,HASH)){
      code {
        (exists EXPR, HASH)
      }
    }
    syntax (case (EXPR,SUB)){
      code {
        SUB(EXPR)
      }
    }

##</code><code>##

    parser = new Parse::RecDescent (q{
        expression: and_expr '||' expression | and_expr
        and_expr:   not_expr '&&' and_expr   | not_expr
        not_expr:   '!' brack_expr           | brack_expr
        brack_expr: '(' expression ')'       | identifier
        identifier: /[a-z]+/i
        });

 # becomes after dropping the quoting operator q{}

    parser = new Parse::RecDescent(
        expression: and_expr '||' expression | and_expr
        and_expr:   not_expr '&&' and_expr   | not_expr
        not_expr:   '!' brack_expr           | brack_expr
        brack_expr: '(' expression ')'       | identifier
        identifier: /[a-z]+/i
        );