Basic Bourne doesn't have regular expressions in the [ command, no. You can use case in this case (sic) though.
Code:
case $reply in [0-9][0-9][0-9][0-9][0-9]) rejoice;; esac
The
case statement uses basic glob patterns, not full regular expressions. The
expr command supports regular expressions, and many modern Bourne-compatible shells have extensions which add regex support to the shell itself.
