Builtin 'read' data not saved

[P Fudd]

Hello all,

I'm at my wit's end.  This script is not working:
=========================================
#!/bin/bash
B=none
echo "2" | while read -r A; do
  B="$A"
  echo 1.B=$B
done
echo 2.B=$B
==========================================
The output, from GNU bash, version 4.2.25(1)-release
(x86_64-pc-linux-gnu), bash-4.2-2ubuntu2.1.deb, is this:

1.B=2
2.B=none

I'm baffled; it's like the while loop is in a parallel universe.  I tried
'export B=none' in line 2, with no effect.

Help?
--
fink@ch.pkts.ca