A correction:

Code:

i=1
while [ i -le 100 ] ; do
  (( i += 1 ))
done
print $i

produces 101 in ksh and errors in Bourne shell.
While the following

Code:

i=1
while [ $i -le 100 ] ; do
  i=`expr $i + 1`
done
echo $i

runs on both,
but might produce 1 in an old Bourne shell because it always runs the while loop in a sub shell.
A later Bourne shell has got a fix, but seeing a redirection it still runs the sub shell.

Code:

i=1
while [ $i -le 100 ] ; do
  i=`expr $i + 1`
done </dev/null
echo $i

That means all Bourne shells do not work with the previously suggested <<EOF redirection.
The Posix shell has got it all fixed. And all Posix-compatible shells.
But a pipe really forces a sub shell. Because it is the last part of the pipe. Compare with a simple command

Code:

echo "a:b:c:" | IFS=":" read a b c

Only the ksh has got the (incompatible) modification to run the last part of the pipe in the current shell.

Back to the initial post - that works only in ksh.
The following is portable to all Posix-compatible shells:

Code:

totalstr=$(
# sub shell starts
  sep=""
  echo "$loc" |
  while IFS= read -r line ; do
    # the pipe might force a sub sub shell
    printf "%s" "$sep$line"
    sep=","
  done
# sub shell ends
)
echo "Final Output:$totalstr "

As you can see, a sub shell inherits everything from the current shell, but not vice versa.