What about using a nested hash instead of the array? That will save you the lookup-loop when updating an element...

my %data;    #  btw.: never call your structure "data" in "real progra
+ms" ;-)

my $mac  = "11:22:33:55:66:77";

$data{$mac}{ap_name} = "AP one";
$data{$mac}{ap_model} = "1131";

my $mac2 = "00:00:00:00:00:00";

if (exists($data{$mac2}) {
    $data{$mac2}{serial} = "FTX12345";
}
[download]

HTH, Rata