#!/bin/perl
use strict;
use warnings;

my @months = ('', qw/jan feb mar apr may jun jul aug sep oct nov dec/); 

print($_, "\t") for @months; 
print "\n"; 

my (%report, $cust);

open(my $DATA, '<', 'sales.txt') or die "Open failed: $!";

while (<$DATA>) {
    chomp; 
    if ( /^[A-Z]/ ) { 
        $cust = $_; 
        @{ $report{$cust} } = map { 0 } @months; 
        next; 
    } 

    my ($date, $value) = split ' ', $_; 
    my ($mon, $year) = split '/', $date; 

    $report{$cust}[$mon] = $value; 
}

foreach my $cust (keys %report) {
    print $keys,"\t"; 
    print($report{$cust}[$_], "\t") for 0 .. 12; 
} 
print "\n"; 

##</code><code>##

}  
print "\n";