Thank you, in part. I have narrowed the problem to the Tk::Entry widget. The 4 and 6 on my keypad are treated as arrow keys regardless of whether numlock is on or not. I'll go peruse some more documentation, I guess!
This probably doesn't apply to Solaris, but I remember from years back doing things like that with PC keyboards and you had to check for a double keystroke - ESC plus the corresponding code for your key.