Procargs makes all the args to a proc accessable via switches.  It is
similar to option handlers for programs, but operates on the proc
level.

usage:

 procargs proc
   This redefines ''proc'' so that all subsequent proc definitions use
   procargs.

 procargs procname
   Changes an existing proc procname to a procargs proc.


 procargs ''procname'' ''args'' ''body''
   define the given proc procname as a procargs proc.



 interp alias {} _proc {} proc

 proc _procargs { __name __params __args } {
    set __nargs [llength $__args]
    set __npars [llength $__params]

    # Set the defaults
    #
    foreach __par $__params {
        set __param     [lindex $__par 0]
        set __value     [lindex $__par 1]

        if { ![string compare $__par args] } {
            set __acat 1
            break
        }

        upvar $__param $__param
        set   $__param $__value
        lappend __paramnames $__param
    }

    # Set the args
    #
    set __p   0
    set __eoo 0
    for { set __i 0 } { $__i < $__nargs } { incr __i } {
        set __arg [lindex $__args $__i]

        if { $__eoo } {
            set __pnum $__p
            incr __p
        } else {
            switch -regexp -- $__arg {
             ^$         -
             ^-[0-9.]+$ -
             ^[^-].*$  {
                set __pnum $__p
                incr __p
             }
             default {
                if { ![string compare $__arg "--"] } {
                    set __eoo 1
                    continue
                }
                set __pnum [lsearch $__paramnames [string range $__arg 1 end]]
                if { $__pnum < 0 } {
                    error "$name: no option $__arg: must be one of: $__paramnames"
                }
                set arg [lindex $__args [incr __i]]
             }
            }
        }

        set __param [lindex $__paramnames $__pnum]
        set $__param $__arg
    }
 }