ref: ec35f468e0eba87c9f09cbbe5fa8af2591e6f914
dir: /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