30-income-calculon.pl

use strict;
use warnings;
use Text::Table;
use List::Util qw(sum);

my $start = 1_000    || $ARGV[0];
my $end   = 100_000  || $ARGV[1];
my $step  = 1_000    || $ARGV[2];

my @data;
for (my $salary = $start; $salary <= $end; $salary += $step) {

    push @data => [
        # Your Gross income
        eurofy($salary),

        # Without 30% ruling
        eurofy(
            tax_each_bucket(
                divide_income_into_tax_buckets($salary),
            )
        ),

        # With a 30% ruling you only pay taxes on 70% of your income
        eurofy(
            sum(
                tax_each_bucket(
                    divide_income_into_tax_buckets($salary * 0.70),
                ),
                $salary * 0.30
            ),
        ),
    ];
}

my $table = Text::Table->new(
    "Gross income\n(before taxes)",
    "Net income\n(after taxes)",
    "Net income\n(after taxes,\nwith 30% ruling)",
);
$table->load(@data);
print $table;
exit;

sub divide_income_into_tax_buckets {
    my ($income) = @_;

    # The tax rate According to Abigail:
    ## 33%     for income up to EUR 18.628
    ## 41.95%  for income between EUR 18.628 and EUR 33.436
    ## 42%     for income between EUR 33.436 and EUR 55.694
    ## 52%     for income above EUR 55.694
    my %bucket_checks = (
        33      => sub { $_[0] < 18_628 },
        '41.95' => sub { $_[0] >= 18_628 and $_[0] < 33_436 },
        42      => sub { $_[0] >= 33_436 and $_[0] < 55_694 },
        52      => sub { $_[0] >= 55_694 }
    );

    my %bucket;
    for my $amount (1..$income) {
        my $in_bucket = 0;
        for my $bucket (keys %bucket_checks) {
            # Brute-force to keep your house warm during winter in
            # Amsterdam.
            if ($bucket_checks{$bucket}->($amount)) {
                die "panic: We already have amount <$amount> in a bucket" if $in_bucket;
                $bucket{$bucket}++;
                $in_bucket = 1;
            }
        }
    }

    return %bucket;
}

sub tax_each_bucket {
    my (%bucket) = @_;

    return sum(
        map {
            apply_tax_rate(
                $bucket{$_},
                $_,
            );
        } keys %bucket
    );
}

sub apply_tax_rate {
    my ($number, $tax_rate) = @_;

    return ($number * ((100 - $tax_rate) / 100));
}

# From perlfaq5
sub commify {
    local $_  = shift;
    1 while s/^([-+]?\d+)(\d{3})/$1,$2/;
    return $_;
}

sub eurofy {
    my ($number) = @_;

    # Round it
    $number = int $number;

    return sprintf("%s EUR", commify($number));
}

sub percentify {
    my ($number) = @_;

    return sprintf "%.02f%%", $number;
}

__DATA__
$ perl 30-income-calculon.pl
Gross income   Net income    Net income
(before taxes) (after taxes) (after taxes,
                             with 30% ruling)
1,000 EUR      670 EUR       769 EUR
2,000 EUR      1,340 EUR     1,538 EUR
3,000 EUR      2,010 EUR     2,307 EUR
4,000 EUR      2,680 EUR     3,076 EUR
5,000 EUR      3,350 EUR     3,845 EUR
6,000 EUR      4,020 EUR     4,614 EUR
7,000 EUR      4,690 EUR     5,383 EUR
8,000 EUR      5,360 EUR     6,152 EUR
9,000 EUR      6,030 EUR     6,921 EUR
10,000 EUR     6,700 EUR     7,690 EUR
11,000 EUR     7,370 EUR     8,458 EUR
12,000 EUR     8,040 EUR     9,228 EUR
13,000 EUR     8,710 EUR     9,997 EUR
14,000 EUR     9,380 EUR     10,766 EUR
15,000 EUR     10,050 EUR    11,535 EUR
16,000 EUR     10,720 EUR    12,304 EUR
17,000 EUR     11,390 EUR    13,073 EUR
18,000 EUR     12,060 EUR    13,842 EUR
19,000 EUR     12,696 EUR    14,611 EUR
20,000 EUR     13,277 EUR    15,380 EUR
21,000 EUR     13,857 EUR    16,148 EUR
22,000 EUR     14,438 EUR    16,917 EUR
23,000 EUR     15,018 EUR    17,686 EUR
24,000 EUR     15,599 EUR    18,456 EUR
25,000 EUR     16,179 EUR    19,225 EUR
26,000 EUR     16,760 EUR    19,994 EUR
27,000 EUR     17,340 EUR    20,738 EUR
28,000 EUR     17,921 EUR    21,444 EUR
29,000 EUR     18,501 EUR    22,151 EUR
30,000 EUR     19,082 EUR    22,857 EUR
31,000 EUR     19,662 EUR    23,563 EUR
32,000 EUR     20,243 EUR    24,270 EUR
33,000 EUR     20,823 EUR    24,976 EUR
34,000 EUR     21,403 EUR    25,683 EUR
35,000 EUR     21,983 EUR    26,389 EUR
36,000 EUR     22,563 EUR    27,095 EUR
37,000 EUR     23,143 EUR    27,802 EUR
38,000 EUR     23,723 EUR    28,508 EUR
39,000 EUR     24,303 EUR    29,214 EUR
40,000 EUR     24,883 EUR    29,921 EUR
41,000 EUR     25,463 EUR    30,626 EUR
42,000 EUR     26,043 EUR    31,333 EUR
43,000 EUR     26,623 EUR    32,039 EUR
44,000 EUR     27,203 EUR    32,745 EUR
45,000 EUR     27,783 EUR    33,452 EUR
46,000 EUR     28,363 EUR    34,158 EUR
47,000 EUR     28,943 EUR    34,865 EUR
48,000 EUR     29,523 EUR    35,571 EUR
49,000 EUR     30,103 EUR    36,277 EUR
50,000 EUR     30,683 EUR    36,983 EUR
51,000 EUR     31,263 EUR    37,689 EUR
52,000 EUR     31,843 EUR    38,395 EUR
53,000 EUR     32,423 EUR    39,101 EUR
54,000 EUR     33,003 EUR    39,807 EUR
55,000 EUR     33,583 EUR    40,513 EUR
56,000 EUR     34,133 EUR    41,219 EUR
57,000 EUR     34,613 EUR    41,925 EUR
58,000 EUR     35,093 EUR    42,631 EUR
59,000 EUR     35,573 EUR    43,337 EUR
60,000 EUR     36,053 EUR    44,043 EUR
61,000 EUR     36,533 EUR    44,749 EUR
62,000 EUR     37,013 EUR    45,455 EUR
63,000 EUR     37,493 EUR    46,161 EUR
64,000 EUR     37,973 EUR    46,867 EUR
65,000 EUR     38,453 EUR    47,573 EUR
66,000 EUR     38,933 EUR    48,279 EUR
67,000 EUR     39,413 EUR    48,985 EUR
68,000 EUR     39,893 EUR    49,691 EUR
69,000 EUR     40,373 EUR    50,397 EUR
70,000 EUR     40,853 EUR    51,103 EUR
71,000 EUR     41,333 EUR    51,809 EUR
72,000 EUR     41,813 EUR    52,515 EUR
73,000 EUR     42,293 EUR    53,221 EUR
74,000 EUR     42,773 EUR    53,927 EUR
75,000 EUR     43,253 EUR    54,633 EUR
76,000 EUR     43,733 EUR    55,339 EUR
77,000 EUR     44,213 EUR    56,045 EUR
78,000 EUR     44,693 EUR    56,751 EUR
79,000 EUR     45,173 EUR    57,457 EUR
80,000 EUR     45,653 EUR    58,133 EUR
81,000 EUR     46,133 EUR    58,769 EUR
82,000 EUR     46,613 EUR    59,404 EUR
83,000 EUR     47,093 EUR    60,040 EUR
84,000 EUR     47,573 EUR    60,676 EUR
85,000 EUR     48,053 EUR    61,312 EUR
86,000 EUR     48,533 EUR    61,948 EUR
87,000 EUR     49,013 EUR    62,584 EUR
88,000 EUR     49,493 EUR    63,220 EUR
89,000 EUR     49,973 EUR    63,856 EUR
90,000 EUR     50,453 EUR    64,492 EUR
91,000 EUR     50,933 EUR    65,128 EUR
92,000 EUR     51,413 EUR    65,764 EUR
93,000 EUR     51,893 EUR    66,400 EUR
94,000 EUR     52,373 EUR    67,037 EUR
95,000 EUR     52,853 EUR    67,673 EUR
96,000 EUR     53,333 EUR    68,309 EUR
97,000 EUR     53,813 EUR    68,945 EUR
98,000 EUR     54,293 EUR    69,581 EUR
99,000 EUR     54,773 EUR    70,217 EUR
100,000 EUR    55,253 EUR    70,853 EUR