@words=$text_body =~ /(\S+)/g;
#compute $start and $end
$newtext=join(" ",@words[$start..$end]);

##</code><code>##

# $start and $window

$i++ while($i<$start && /(\S+\s+)/g);

$i=0;
while(/\G(\S+\s+)/g && $i<$window_length)
{
    $newtext .= "$1";
    $i++;
}