The answer to your question is that you just add the array subscripting to what you're already dereferencing:

$sheet{$_}->{data}[$column];
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But I think your problem is better suited to arrays of arrays:

use strict;
use warnings;

my @columns = split ' ', <DATA>; # First row is column headers
my @data = map { [ split ' ', $_ ] } <DATA>; # Other rows are data

print "@columns Total\n";
# First column is not numeric, an extra numeric column is
# on the right for the total of the row totals
my @column_totals = ('Total', (0) x @columns-1, 0);
for my $row (@data) {
    my $row_total = 0;
    for my $col (1..$#columns) {
        $row_total += $row->[$col];
        $column_totals[$col] += $row->[$col];
    }
    print "@$row $row_total\n";
    # Last column of column totals is sum of row totals
    $column_totals[$#column_totals] += $row_total;
}
print "@column_totals\n";
__DATA__
employee Buffalo Cleveland
Terry 5.00 2.00
Doug 4.00 3.00
Fred 1.00 5.00
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