} # real datafiles
    my ($basename) = ( $filename =~ m/^(\S+)\.txt/ ) or warn;
##</code><code>##

    printf "        D + C: \t%15s%16s\n",
      &big_money(
        ( $saldi{$filename}{'"D"'} * -1 ) + ( $saldi{$filename}{'"C"'} ) ),
      &big_money($deltaSum);
} #sample

##</code><code>##

#!/usr/bin/perl -w
use strict;
use diagnostics;
use vars qw ! %saldi $filename !;

#chdir  # real code
#  '/Users.......'    # real code
#  or die "Cannot open : $!";                                #real code
#foreach my $filename ( glob "*.txt" ) {    # real code       
#    open FILE, '<', $filename or warn "Can't open FILE: $!";#real code
#    while (<FILE>) {                                        #real code
#        chomp;                                              #real code
#        next unless $_;                                     #real code

while (<DATA>) {    # Required for sample code
     chomp;          # Required for sample code
     next unless $_; # Required for sample code
     $filename = $1, next if /(\w+\.txt)$/; # Required for sample code

        my @fields = ( split /,/, )[ 0, 1, 2, 3, 4 ];
        my ( $account, $currency, $year, $dofc, $amount ) = @fields;
        next unless $dofc && $amount;
        $saldi{$filename}{$dofc} += $amount;    # file name as primary key
    }

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

    foreach $filename ( keys %saldi ) {
        $cSum += $saldi{$filename}{'"C"'};
        $dSum += $saldi{$filename}{'"D"'} * -1;

        my $delta =
          ( $saldi{$filename}{'"D"'} * -1 ) + $saldi{$filename}{'"C"'};
        $deltaSum += $delta;
 #} real   
    my ($basename) = ( $filename =~ m/^(\S+)\.txt/ ) or warn;
    printf "$basename\n";

    printf "\tD sum: \t%16s",
      &big_money( $saldi{$filename}{'"D"'} * -1 ) . "\n";
    printf "\tC sum: \t%16s", &big_money( $saldi{$filename}{'"C"'} ) . "\n";

    printf "        D + C: \t%15s%16s\n",
      &big_money(
        ( $saldi{$filename}{'"D"'} * -1 ) + ( $saldi{$filename}{'"C"'} ) ),
      &big_money($deltaSum);
} #sample
#    close FILE or warn "Can't close FILE: $!";    # real code
#}    # real code

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
394,eur,2006,"C",16
Data_2.txt
494,eur,2006,"C",25
494,eur,2006,"D",79
494,eur,2006,"D",79
494,eur,2006,"D",79
494,eur,2006,"C",100
494,eur,2006,"C",1