ref: fb7dd4b3a868cb8987049c95bb32e6425a73c8b9
dir: purgatorio/libtk/radio.tk
radiobutton .u -text {Upper case} -variable case -value u
radiobutton .l -text {Lower case} -variable case -value l
radiobutton .i -text {Ignore case} -variable case -value i
pack .u .l .i -anchor w -fill x