ksh function problem with backticks

Issue

• Application scripts are working fine with RHEL5.4 (ksh-20080202-14.el5), it doesn't work on RHEL5.5-5.9 and RHEl6.1-4 version of ksh.

• In the later ksh version it works only when we add the eval builtin function. It also works if there is no backticks on the output file of date command.

• In the script reproducer, we are expecting a [[ success == success ]] contrary to [[ '' == success ]] as shown in the debugging output.

• Reproducer script:

$ cat /tmp/jj.sh
#!/bin/ksh

a_func ()
{
        date  > /tmp/example.`date +%Y`
        print "success"
}

if [[ `a_func` = success ]]; then
  echo "success."
else
  echo "failed."
fi

• On RHEL6:

$ rpm -qa |grep ksh
ksh-20100621-19.el6.x86_64

$ ksh -x /tmp/jj.sh
+ a_func
+ date
+ + date +%Y
1> /tmp/example.2013
+ print success
+ [[ '' == success ]]
+ echo failed.
failed.

• On RHEL5.4:

$ rpm -qa |grep ksh
ksh-20080202-14.el5

$ ksh -x /tmp/jj.sh
+ a_func
+ date
+ + date +%Y
1> /tmp/example.2013
+ print success
+ [[ success == success ]]
+ echo success.
success.