[Scribus] how to use "alternative printer command" ?

[Zhang Weiwu]

On the printing dialogue there is an option "alternative printer 
command", click on it the user could input something onto a text box.

How does anyone use it? I tried to fill "/usr/bin/lpr", "/usr/bin/lpr 
$1", "/usr/bin/lpr %" all of them does not print, but on my Gentoo Linux 
if I don't use alternative printer command it prints fine.

Could not find the usage on Google.