#!/usr/bin/perl

use strict;
use warnings;

my $from = 2000;
my $till = 3000;

my @nums;
for my $x (0 .. 9) {
    for my $y ($x .. 9) {
        for my $z ($y .. 9) {
            my %seen;
            push @nums => [grep {!$seen {$_} ++}
                           map  {s/^0{1,2}//; $_} "$x$y$z", "$x$z$y", 
+"$y$x$z",
                                                  "$y$z$x", "$z$x$y", 
+"$z$y$x"]
        }
    }
}


sub all_sub_sets;
sub all_sub_sets {
    return unless @_;

    my $f = shift;
    my @r = all_sub_sets @_;

    @r => [$f] => map {[$f => @$_]} @r
}

my %answers;
foreach my $num (@nums) {
    my @sets = all_sub_sets @$num;

    foreach my $set (@sets) {
        local $" = " + ";
        my $sum  = eval "@$set";
        if ($sum >= $from && $sum < $till) {
            push @{$answers {$sum}} => $set;
        }
    }
}
        
for my $sum ($from .. $till - 1) {
    local $" = " + ";
    print "$sum = @{$answers{$sum}[0]}\n"
                 if $answers {$sum} && 1 == @{$answers {$sum}};
}
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