#!/bin/ksh

typeset num;

for iter in 1 2 3 4 5 6 7 15 123
do
   varb="test$(printf "%02d" ${iter})"
   vara="${varb}_count"
   # increment vara
   #
   num=$(printf "%02d" $(( $(echo "${vara}" | sed -e 's/^[^0-9]*\([0-9][0-9]*\)_.*/\1/') + 1 )) )
   echo "varb->[${varb}] vara->[${vara}] incrementedNum->[${num}] incrementedVarA->[test${num}_count]"
done;