Description of problem:
when eval a string which include "$?" shell variable , result is not right.

Version-Release number of selected component (if applicable):
# uname -r
2.6.32-279.el6.x86_64
# rpm -q mksh
mksh-39-7.el6.x86_64
# rpm -q ksh
ksh-20100621-16.el6.x86_64
# rpm -q bash
bash-4.1.2-9.el6_2.x86_64


Steps to Reproduce:
1. In mksh :

# /bin/mksh -c 'echo $KSH_VERSION;STRING="[ \$? -eq 0 ] && echo EXEC OK || echo EXEC ERR";./bad_cmd;eval $STRING'
@(#)MIRBSD KSH R39 2009/08/01
/bin/mksh: ./bad_cmd: not found
EXEC OK


2. In ksh :

#  /bin/ksh -c 'echo $KSH_VERSION;STRING="[ \$? -eq 0 ] && echo EXEC OK || echo EXEC ERR";./bad_cmd;eval $STRING'
Version JM 93t+ 2010-06-21
/bin/ksh[1]: ./bad_cmd: not found [No such file or directory]
EXEC ERR

3. In bash :

#  /bin/bash -c 'echo $BASH_VERSION;STRING="[ \$? -eq 0 ] && echo EXEC OK || echo EXEC ERR";./bad_cmd;eval $STRING'
4.1.2(1)-release
/bin/bash: ./bad_cmd: No such file or directory
EXEC ERR


Actual results:
mksh have not the same behavior than ksh (and bash)

Expected results:
return code must be different than 0 for this eval of a bad cmd