can't read "argv0": no such variable
    while executing
"open $argv0"
    (in namespace eval "::request" script line 3)
    invoked from within
"namespace eval ::request $script"
    ("::try" body line 12)
OUTPUT BUFFER:
#!/usr/local/bin/wish

set fd [open $argv0]
set txt [read $fd]
close $fd

if {$argc == 0} {
    set n 5
} else {
    set n [lindex $argv 0]
}
set data "[string repeat $txt $n]"

for {set i 0} {$i < [string length $data]} {incr i 20} {
    lappend offsets $i [expr $i + 10]
}

proc markdata {str off} {
    set prev 0
    set ldata [list]
    foreach {s e} $off {
	if {$prev < $s} {
	    lappend ldata [string range $str $prev [expr $s -1]] {}
	}
	lappend ldata [string range $str $s [expr $e - 1]] TEST
	set prev $e
    }
    return $ldata
}

set data2 [markdata $data $offsets]

# data exists - just add tags
proc p1 {txt off} {
    $txt tag remove TEST 1.0 end
    set cmd [list $txt tag add TEST]
    foreach {s e} $off {
	lappend cmd [$txt index "1.0 + $s c"] [$txt index "1.0 + $e c"]
    }
    eval $cmd
    update
}

# delete & re-add text
proc p2 {txt off} {
    set str [$txt get 1.0 end]
    $txt delete 1.0 end
    set args [markdata $str $off]
    eval $txt insert end $args
    update
}

# have text in memory
proc p3 {txt str off} {
    $txt delete 1.0 end
    set args [markdata $str $off]
    eval $txt insert end $args
    update
    puts ">>$args<<"

}

# can have data pre-built
proc p4 {txt data} {
    $txt delete 1.0 end
    eval $txt insert end $data
    update
}

proc timers {} {
    global ITER offsets data data2
    
    puts "Timing with $ITER iterations ([string length $data] characters and [expr {[llength $offsets]/2}] tagged regions)"
    puts -nonewline "  Proc p1 : "
    puts [format "%8.6f seconds" [expr [lindex [time { p1 .t $offsets} $ITER] 0] / 1000000.0]]
    puts -nonewline "  Proc p2 : "
    puts [format "%8.6f seconds" [expr [lindex [time { p2 .t $offsets} $ITER] 0] / 1000000.0]]
    puts -nonewline "  Proc p3 : "
    puts [format "%8.6f seconds" [expr [lindex [time { p3 .t $data $offsets} $ITER] 0] / 1000000.0]]
    puts -nonewline "  Proc p4 : "
    puts [format "%8.6f seconds" [expr [lindex [time { p4 .t $data2} $ITER] 0] / 1000000.0]]
    puts "Testing Complete\n"
}

text .t -yscrollcommand ".s set"
scrollbar .s -command ".t yview"
frame .f1
button .f1.p1 -text "p1" -command [list p1 .t $offsets]
button .f1.p2 -text "p2" -command [list p2 .t $offsets]
button .f1.p3 -text "p3" -command [list p3 .t $data $offsets]
button .f1.p4 -text "p4" -command [list p4 .t $data2]
frame .f2
entry .f2.e -textvar ITER
set ITER 10
button .f2.b -text "Run Timing" -command timers

pack .f2 .f1 -side bottom -fill x
pack .s -side right -fill y
pack .t -expand 1 -fill both

pack .f1.p1 .f1.p2 .f1.p3 .f1.p4 -side left -expand 1 -fill none
pack .f2.e .f2.b -side left -expand 1 -fill none

.t insert end $data
.t tag config TEST -background red

update
timers
exit