You might be able to just use the Ungroup function I referred to. For example, get the address of the cell you want, and do $ws->Range("A1")->Ungroup();

Note that the range is a normal Perl string, so you can easily iterate over a number of cells:

# Pardon the C-ish loop, it's late.
for (my $row = 1; $row <= 10; $row++) {
    $ws->Range("A$row")->Ungroup();
}
# or an alternate if you have an area:
# (cell addresses off the top of my head)
$ws->Range("A1:D46")->Ungroup();
[download]

Note that I haven't had to use this function myself, so I'm not 100% positive it's the function you need. But you should be able to do some quick tests -- and look at the help for the function to see what can unmerge cells.