Itcl

package require Itcl

itcl::class Counter {
    private variable count 0

    constructor {{start 0}} {
        set count $start
    }

    method increment {{by 1}} {
        incr count $by
    }

    method decrement {{by 1}} {
        incr count -$by
    }

    method reset {} {
        set count 0
    }

    method value {} {
        return $count
    }
}

set c [Counter #auto]
puts "Initial value: [$c value]"
$c increment
$c increment
$c increment 5
puts "After increments: [$c value]"
$c decrement 2
puts "After decrement: [$c value]"
$c reset
puts "After reset: [$c value]"
itcl::delete object $c