Valid strings are any single-character string, or any of the following strings:
f1, f2, f3, f4, f5, f6, f7, f8, f9, f10, f11, f12,
f13, f14, f15, f16, f17, f18, f19, f20,
pad., pad*, pad+, pad/, pad-, pad=,
pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7, pad8, pad9,
padclear, padenter
return, tab, space, delete, escape, help,
home, pageup, forwarddelete, end, pagedown,
left, right, down, up,
shift, rightshift, cmd, rightcmd, alt,
rightalt, ctrl, rightctrl, capslock, fn