Dial - an alternative to the scale widget
 use Tk::Dial;
 $dial = $top->Dial(-margin =>  20,
                    -radius =>  48,
                    -min    =>   0,
                    -max    => 100,
                    -value  =>   0,
                    -format => '%d');
 margin - blank space to leave around dial
 radius - radius of dial
 min, max - range of possible values
 value  - current value
 format - printf-style format for displaying format
Values shown above are defaults.
A dial looks like a speedometer: a 3/4 circle with a needle indicating
the current value.  Below the graphical dial is an entry that displays
the current value, and which can be used to enter a value by hand.
The needle is moved by pressing button 1 in the canvas and dragging. The
needle will follow the mouse, even if the mouse leaves the canvas, which
allows for high precision. Alternatively, the user can enter a value in
the entry space and press Return to set the value; the needle will be
set accordingly.
 Configure
 Tick marks
 Step size
Roy Johnson, rjohnson@shell.com
Based on a similar widget in XV, a program by John Bradley,
bradley@cis.upenn.edu
 
August 1995: Released for critique by pTk mailing list