It is commendable that you're calling system with an array of references, because that avoids some of the shell exploits.

However, since you intend to use shell redirection to accomplish your command, you can't do it this way.

The easy way to do it would be:

system("$tar $taropts $backupdir | $ssh $user\@$remotehost 'dd of=$rem
+otedir/back.tar.gz'")
[download]

The hard way would be starting tar in one process, the ssh/dd in another, and playing the IPC between them. Comparatively hard, for very little gain.

In effect, you'd have to reimplement the shell redirects in order to do it. It's easier to just use the shell's redirects, and fortunately, Perl makes that possible.