Assuming @data is the array you want to check for 5 indentical (string) values in a row:

my $c = 0;
for (my $i = 1; $i < @data; $i ++) {
    if ($data[$i] eq $data[$i - 1]) {
        if (++$c >= 4) {
            print "Five indentical values in a row, starting at positi
+on ", $i - 4, "\n";
        }
    }
    else {
        $c = 0;
    }
}
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