foreach( @{$result->MetricAlarms} ){

        print "-"x79,"\n";
        print "**AlarmName** : ", $_->AlarmName,"\n";
        print Dumper($_);
    }
    print "\n***\n--number of elements: ", scalar @{$result->MetricAlarms}, "\n";

##</code><code>##

my $ar_ref = $result->MetricAlarms;
foreach( @$ar_ref ){
...