Description of problem:

command substitution appears to not work when preceded by a "|" redirection


Version-Release number of selected component (if applicable):
Name        : ksh                          Relocations: (not relocatable)
Version     : 20100621                          Vendor: Red Hat, Inc.
Release     : 19.el6_4.4                    Build Date: Thu 16 May 2013 09:25:18 AM EDT

How reproducible:

try to use command substitution after a pipe, here's a silly example:

# echo blah | echo  $(hostname)

#

Steps to Reproduce:

1.run:
# echo blah | echo  $(hostname)
2. look at the empty (carriage return) output.
3.

Actual results:

blank output (command substitution doesn't work)

Expected results:
output should be what the command "hostname" would output on it's own

Additional info:

here's a more through silly example:
# echo $(hostname)
pchd
# echo blah ; echo  $(hostname)
blah
pchd
# echo blah | echo  $(hostname)

(variable expansion does work, it seems only command substitution does not work)

# echo blah | echo  $HOSTNAME  
pchd
# 

in rhel5:

[root@rhel5-test ~]# ksh
# echo blah | echo $(hostname)
rhel5-test
# 

note: this appears to be a side-effect of 927586, but this is just guessing, i have no proof or explanation (feel free to ignore this assumption)

the impact to the customer is significant, this is a major change in behaviour, and it breaks many of their existing (tested, productive) scripts