dbx adds the following features as extensions:
$[ p -> flags ] language expression
typeset --q enables special quoting for user-defined functions
csh-like history and alias arguments
-set +o path disables path searching
0xabcd C syntax for octal and hexadecimal numbers
bind to change Emacs-mode bindings
set --o hashall
set --o ignore suspend
print --e and read --e (opposite of --r, raw)
built-in dbx commands