lets say you wanted the 2nd element of array @hello to be hi..then you could do something like

$hello[1] = 'hi';
[download]

thats all this is doing..lets say we have this

my @first = qw/one two three/;
my @second = qw/four five six/;

for $value(@first){
    $second[++$#second] = $value;
}
[download]

so $#second starts out as 2 (the number of elements in $second starting from zero) so the ++$#second is saying start at 3. So during the first loop its basically saying

$second[3] = $value;
[download]

so we're appending the elements of @first to @second, which in the end will contain 'four five six one two three' in my example..an easier way would have been to just do

push(@second, @first);
[download]

but i guess the docs were trying to make a point (too lazy to go look for myself (: )..anyway, hope this helps clear things up a bit for you

-Robert