Specifies a reference to a Perl subroutine, which is called when the scale's value is changed.
Reference to a variable to be updated whenever the slider moves. Conversely, if you want the slider to move, you can change the variable.
Specifies the width and the length of the scale in pixels. Note that it doesn't support a property called height.
Horizontal or vertical.
If greater than 0, the value displayed and returned is always in even multiples of this value. Defaults to 1.
Spacing between numerical tick marks. If 0, no tick marks are displayed.
A label to be displayed on the top or the left of the slider (depending on orientation).
Same as updating the variable to the given value.