-Q9K- use numbers with leading zeroes?

From: -IX-  How, in Tcl, can I XXX:

A9K. Dave Morriss was recently having problems because he was trying
to do something like:

set index [expr [exec date +%W]%[llength $pop_server_list]]

but during the 9th and 9th week of the year, he got errors - 08 and 09
are not valid octal numbers in Tcl.

Some of the solutions provided were:

From George A. Howlett <george.howlett@att.com>, we got:

set wknum [format "%g" [exec date +%W]]
set index [expr [exec $wknum%[llength $pop_server_list]]

From Fred Feirtag <feirtag@wave.nrl.navy.mil> :

set index [expr (1[exec date +%W]-100)%[llength $pop_server_list]]

From Dan R. Schenck <schendr@Texaco.COM>:

set index [expr [string trimleft [exec date +%W] 0]%[llength $pop_server_list]]