This is one way to do it without a hash table. Your grouping constraints can be enforced by sorting the table. then roll through the table doing sums and printing every time the grouping changes.
use strict;
use warnings;
use Data::Dump qw(pp);
use constant { "AcctName" => 0, "EntityName" => 1, "UnitName" => 2};
my @array = (
['Account01', 'Entity01', 'Unit01', 1, 2,
+3],
['Account01', 'Entity01', 'Unit01', 4, 5,
+6],
['Account02', 'Entity02', 'Unit02', 10, 11,
+ 12],
['Account01', 'Entity01', 'Unit01', 7, 8,
+9] );
@array = sort {$a->[AcctName] cmp $b->[AcctName]
or
$a->[EntityName] cmp $b->[EntityName]
or
$a->[UnitName] cmp $b->[UnitName] }@array;
pp \@array;
die "input array too small!!" unless @array>=2;
my $firstRowRef = shift @array;
my @startRow = @$firstRowRef;
foreach my $row_ref (@array)
{
my @curRow = @$row_ref;
if ($curRow[0] ne $startRow[0] or
$curRow[1] ne $startRow[1] or
$curRow[2] ne $startRow[2] )
{
print "@startRow\n"; # new grouping
@startRow = @curRow;
}
else # group continuation
{ # add current month #'s to totals
$startRow[3]+=$curRow[3];
$startRow[4]+=$curRow[4];
$startRow[5]+=$curRow[5];
}
}
print "@startRow\n"; # This is for the last row of array
__END__
sorted array is:
[
["Account01", "Entity01", "Unit01", 1, 2, 3],
["Account01", "Entity01", "Unit01", 4, 5, 6],
["Account01", "Entity01", "Unit01", 7, 8, 9],
["Account02", "Entity02", "Unit02", 10, 11, 12],
]
Account01 Entity01 Unit01 12 15 18
Account02 Entity02 Unit02 10 11 12