Package review of the new tcsh617 package including a patch for this bz was successful. See bug 676136.
*** Bug 689383 has been marked as a duplicate of this bug. ***
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.
Previously, when a command was substituted using backquotes, a second, redundant fork() system call was performed. This could have caused problems when a child process needed to find the PID of its tcsh parent. With this new package, only one fork() is performed.
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.