When I run your code with the following values:

my $key="test";
my %matrixhash=('test'=>'camel');
my $store="store me";
[download]

it correctly reponds with "Key exists ! ". Your code as given is correct. Are you sure that $key contains what you expect it to contain?

Perhaps if you post some more code, the problem might become more apparent.

CU
Robartes-