How to assemble several areas in one image to get a new image? using Composite()? How?

Hi Everybody,

I'm new to ImageMagick and haven't figured out how to assemble several areas
into a new image.
E.g., I know the "geometry" of words "hello" and "world" respectively in an
image, what I need to do
is to retrieve the word images and put then into one line image while keep
their relative positions.

Question1: Suppose I use the perl API, how should I use Composite() or other
correct methods to do this?
......
my $geom = sprintf('%dx%x+%d+%d', $word->{width}, $word->{height}, $offsetx,
$offsety);
$x = $lineimg->Composite($wordimg, $geom);
warn "$x" if "$x";
......

Suppose $lineimg's size is big enough to hold all word images and the
geometry has been computed.
This code gives out a complain by ImageMagick:

Exception 410: composite image required `Image::Magick' @
Magick.xs/XS_Image__Magick_Mogrify/7790 ...

Question2: currently I only know how to crop a word image out of the
original one and then Clone() method
to restore the original image. Is there a way to copy instead of crop a
specific area from a image? This way
can save the time to copy back and forth the whole image several times.

Does anybody know how to write this kind of processing? I appreciate all
your help and suggestions!

-J.C.