No need to use an array, you just need to store two values, the total and the count: 

my %vals_by_type;
while ( <DATA> ) {
    my ( $type, $val ) = split;
    $vals_by_type{ $type }{ total } += $val;
    $vals_by_type{ $type }{ count }++;
}


for my $type ( sort keys %vals_by_type ) {
    my $avg = $vals_by_type{ $type }{ total } / $vals_by_type{ $type }
+{ count };
    printf "%s %.2f\n", $type, $avg;
}

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In reply to Re^2: HOW to calculate the column data by jwkrahn
in thread HOW to calculate the column data by xbmy

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