#!/usr/local/bin/perl
# day 2015-06

use strict;
use warnings;
use v5.32;

@ARGV = "input" unless @ARGV;
chomp( my $input = do { local $/; <> } );

my @strings = split /\n/, $input;
my %lights;
foreach my $x ( 0 .. 999 ) {
    foreach my $y ( 0 .. 999 ) {
        $lights{ $x, $y } = -1; # set to off
    }
}

foreach ( @strings ) {
    my ( $instructions, $from, $to ) =
        m/(off|on|toggle)\s(\d+,\d+) through (\d+,\d+)/;
    my ( $from_x, $from_y ) = split /,/, $from;
    my ( $to_x, $to_y )     = split /,/, $to;
    for ( my $x = $from_x; $x < $to_x + 1; $x++ ) {
        for ( my $y = $from_y; $y < $to_y + 1; $y++ ) {
            $lights{ $x, $y }  = -1 if ( $instructions eq 'off' );
            $lights{ $x, $y }  = 1  if ( $instructions eq 'on' );
            $lights{ $x, $y } *= -1 if ( $instructions eq 'toggle' );
        }
    }
}

say "part 1: ", scalar grep { $_ > 0 } values %lights;