fours.pl

#!/usr/bin/perl

use strict;
use warnings;

my $str = "44+4 = 444/4-44/4+4/4";

sub main(){
	for my $i (0,1,7,8,9,13) {
		my $copy = $str;
		my $char = "".substr($copy, $i, 1);
		substr($copy, $i, 1) = "";
		
		for my $j (0..20) {
			my $copy1 = $copy;
			substr($copy1, $j, 0) = $char;
			my ($left, $right) = split '=', $copy1;
			my $l = eval $left;
			my $r = eval $right;
			if(defined $l && defined $r && $l == $r){
				print "\n$copy1\n";
				print "$l = $r\n";
			}
		}
		
		for my $j (0..20) {
			my $copy1 = $copy;
			substr($copy1, $j, 0) = "**$char";
			my ($left, $right) = split '=', $copy1;
			my $l = eval $left;
			my $r = eval $right;
			if(defined $l && defined $r && $l == $r){
				print "\n$copy1\n";
				print "$l = $r\n";
			}
		}
	}
}

main();