regexp help

Shell Programming and Scripting
1

I'd like to know if there is a catchall line for renaming the following patterns:

s01e03 -> 01x03
s4e9 -> 04x09
s10e08 ->10x08

and possibly even:
318 -> 03x18
1002 ->10x02
if its the first 3 or first digit number in the string.

thanks!