Why bother doing all that work when someone else has already done it for you? I think you'll find the List::Util module in the Scalar-List-Utils bundle will do all you want.

use List::Util;

# assume data in @data
my $max = max @data;
my $min = min @data;
my $sum = reduce { $a + $b } @data;
my $avg = $sum / @data;
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