syntactically corrected

set texto {<A texte of 700 000 words>}
set text [split $texto]
for {set a 1; set b 0 ; set c 7000} {$c < 400000} {incr a 1 ; incr b 3 ; incr c 3} {
   set textChunks($a) [lrange $text $b $c]
}