Known bugs:

EXPR: || and && are not lazy. ?: is not implemented. Double math not
      implemented. Functions like sin(), cos(), not implemented.

jim::libPath variable is accessed in the local context instead than
globally, so the [load] command will fail inside procs.

[subst] ingores special meaning of JIM_BREAK and alike.

[info level ?level?] takes the level argument like [uplevel], but
it should be different, positive is absolute, negative is relative.