To simply start to debug then execute that ksh script in debug mode as,

ksh -x <script.ksh>

it will give appropriate location where it is getting problem.

You can not work for loop as lik fore ((y=0; y<=${#fName[*]}; y++)) in shell script so that you can use while instead of it as,

y=0
while [[ $y -le ${#fName[*]} ]]
do
action;;
let y=y+1
done

It will do that trick.

HTH.