TCL & TMSH command > unexpected argument "|" while using grep

Not at all the prettiest thing in the world, but try this:

proc script::run {} {
    set order 0
    foreach x [split [tmsh::list apm all-properties] "\n"] {
        if { [string trimleft $x] starts_with "acl-order" } {
            set num [lindex [split [string trimleft $x]] 1]
            if { [expr { $num > $order }] } {
                set order $num
            }
        }
    }
    puts "largest: $order"
}

This will loop through each line of the tmsh command's result, find acl-order and its value, and then return the largest number.