nested exec<<HERE ambiguity

[klausf]

Configuration Information [Automatically generated, do not change]:
Machine: sparc
OS: solaris2.5.1
Compiler: /opt/local/bin/gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DHOSTTYPE='sparc' 
-DOSTYPE='solaris2.5.1' -DMACHTYPE='sparc-sun-solaris2.5.1' -DSHELL 
-DHAVE_CONFIG_H -DSunOS5  -I. -I. -I./lib -g -O2
uname output: SunOS matlock 5.6 Generic_105181-13 sun4u sparc SUNW,Ultra-1
Machine Type: sparc-sun-solaris2.5.1

Bash Version: 2.02
Patch Level: 0
Release Status: release

Description:
        When bash sources (`.') the file whose contents is given after the
        "Repeat-By:" line, it doesn't echo a `1' like the bourne and korn
        shells do. I'm not sure which output is correct. If the file is
        used as a shell script, there's no visible difference.

Repeat-By:
exec<<a
exec<<b
echo 2
b
echo 1
a
echo 0