Just some small tweaks to make it work. 

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11146593
use warnings;

my @mapped = ("Account Entity Unit Jan Feb Mar",
            "Account01 Entity01 Unit01 1 2 3",
            "Account01 Entity01 Unit01 4 5 6",
            "Account01 Entity01 Unit01 7 8 9",
            "Account02 Entity02 Unit02 10 11 12");

my %group_by;
my @titles = split ' ', shift @mapped;

foreach (@mapped) {
    my %hash; @hash{ @titles } = split;   #don't get it NOTE makes a h
+ash with titles as keys and fields of current line as values
    for(qw(Jan Feb Mar)){
        $group_by{join ' ', @hash{qw(Account Entity Unit)}}{ $_ } += $
+hash{ $_ };    #don't get it either NOTE does the SUM function that y
+our SQL is doing
    }
}
use Data::Dump 'dd'; dd \%group_by;

[download]

Outputs: 

{
  "Account01 Entity01 Unit01" => { Feb => 15, Jan => 12, Mar => 18 },
  "Account02 Entity02 Unit02" => { Feb => 11, Jan => 10, Mar => 12 },
}

[download]

In reply to Re^4: Group by from array by tybalt89
in thread Group by from array by sroux

Title:
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