#!/bin/sh -v
echo hoge | awk '
BEGIN {
		column = "A"
		alphabet =  "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
		
		for (i = 1; i <= 30; i++) {
			for (j = length(column); j >= 1; j--) {
				k = (index(alphabet, substr(column, j, 1)) % 26) + 1;
				column = substr(column, 1, j - 1) substr(alphabet, k, 1) substr(column, j +1);
				print column;

				if (k > 1) {
					break;
				}
			}

			if (j == 0) {
				column = "A" column;
			}
		}
}
'