#!/usr/bin/perl -w
use strict;
my %columns = (
    1 => 1,
    2 => 1,
    3 => 1,
    4 => 1
);

my @discounts = qw( 1 2 1 3 1 4 1 5);

for my $discount (@discounts) {
    if ($discount == 1) {
        my $key_num = scalar keys %columns;
        $key_num++;
        $columns{$key_num} = 1;
    }
}
print "$_ : $columns{$_}\n" foreach (keys %columns);