Hi, thanks for the explanation. I understand your explanation, but I've checked thru my codes but ca'nt see such mistake being committed. The only (write) operations I've done to the arrays (prior to discovering the problem) is shown below. What I am trying to do is to remove duplicate entries (based on certain column combinations) and store them in a new array (those with the "unique" prefix). The "cross-referencing" seems to have been committed here. 
my %seen_values;
my @unique_terminal_id = grep { !($seen_values{$_->[4]}++) } @temp_ope
+n_single;
my %seen_values;
my @unique_manufacturer_model = grep { !($seen_values{$_->[9]}{$_->[10
+]}++) } @unique_terminal_id;
my %seen_values;
my @unique_manufacturer_model_version = grep { !($seen_values{$_->[9]}
+{$_->[10]}{$_->[11]}++) } @unique_terminal_id;

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In reply to Re^2: Updating 1 array affects the other array by iphony
in thread Updating 1 array affects the other array by iphony

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