#!/usr/bin/perl
use strict;

my %saldi;
my $file;

while (<DATA>) {
    chomp;
    next unless $_;
    $file = $1, next if /(\w+\.txt)$/; # Required for sample code only
    
    my @cellen = ( split /,/, )[ 3, 4 ];
    next unless $cellen[0] && $cellen[1];
    $saldi{$file}{ $cellen[0] } += $cellen[1]; # file name as primary key
}

my $dSum = 0;
my $cSum = 0;
my $deltaSum = 0;

foreach my $filename ( keys %saldi ) {
    $cSum += $saldi{ $filename }{ C };
    $dSum += $saldi{ $filename }{ D };

    my $delta = $saldi{ $filename }{ D } - $saldi{ $filename }{ C };
    $deltaSum += $delta;
    printf "$filename delta:\t%8s\n", big_money( $delta );
}

printf "C sum:    \t%16s\n", &big_money( $cSum );
printf "D sum:    \t%16s\n", &big_money( $dSum );
printf "Delta sum:\t%16s\n", &big_money( $deltaSum );

sub big_money { #Learning Perl
    my $number = sprintf "%.2f", shift @_;

    #Add one comma each time though the do-nothing loop
    1 while $number =~ s/^(-?\d+)(\d\d\d)/$1,$2/;

    #Put the dollar sign in the right place
    $number =~ s/^(-?)/$1/;
    $number;
}

__DATA__
Data_1.txt
394,eur,2006,D,18.20
394,eur,2006,D,22
394,eur,2006,C,25
Data_2.txt
494,eur,2006,C,25
494,eur,2006,D,79

##</code><code>##

Data_1.txt delta:	   15.20
Data_2.txt delta:	   54.00
C sum:    	           50.00
D sum:    	          119.20
Delta sum:	           69.20