per里switch的应用

    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 (\&sub)    { print "arg to subroutine" }
        else            { print "previous case not true" }
    }