Namespace problem with pipe into a braced group

[tobi]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc -I/usr/src/packages/BUILD/bash-3.1 
-L/usr/src/packages/BUILD/bash-3.1/../readline-5.1
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' 
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-suse-linux-gnu' 
-DCONF_VENDOR='suse' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL 
-DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib   -O2 -fmessage-length=0 -Wall 
-D_FORTIFY_SOURCE=2 -g -D_GNU_SOURCE -DRECYCLES_PIDS -Wall -pipe -g -fPIE 
-fbranch-probabilities
uname output: Linux t60 2.6.18.8-0.13-default #1 SMP Thu Nov 6 13:35:13 UTC 
2008 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-suse-linux-gnu

Bash Version: 3.1
Patch Level: 17
Release Status: release

Description:
        I would have expected the output to be 2 in both cases.  My mistake or 
yours?  :-)

Repeat-By:
        a=1; echo foo;{ a=2; }; echo $a         # output: 2
        a=1; echo foo|{ a=2; }; echo $a         # output: 1

        Bug or feature?