I suspect he used something slow to emulate sets in Perl 5. I get:

    $ time python3 send.py 
    9567 + 1085 = 10652

    real	0m16.388s
    user	0m16.299s
    sys	0m0.049s

    $ time perl send.pl 
    9567 + 1085 = 10652

    real	0m16.838s
    user	0m16.732s
    sys	0m0.063s

With:

    use strict;
    use warnings;
    
    my %digits = map { $_ => 1 } ( 0 .. 9 );
    
    sub choose ($&) {
        my ( $set, $sub ) = @_;
        map { $sub->($_) } grep { $set->{$_} } keys %$set;
    }
    
    sub guard { $_[1]->() if $_[0] }
    
    choose { %digits, map { $_ => 0 } ( 0 ) }, sub { my $s = $_[0];
    choose { %digits, map { $_ => 0 } ( $s ) }, sub { my $e = $_[0];
    choose { %digits, map { $_ => 0 } ( $s, $e ) }, sub { my $n = $_[0];
    choose { %digits, map { $_ => 0 } ( $s, $e, $n ) }, sub { my $d = $_[0];
    choose { %digits, map { $_ => 0 } ( 0, $s, $e, $n, $d ) }, sub { my $m = $_[0];
    choose { %digits, map { $_ => 0 } ( $s, $e, $n, $d, $m ) }, sub { my $o = $_[0];
    choose { %digits, map { $_ => 0 } ( $s, $e, $n, $d, $m, $o ) }, sub { my $r = $_[0];
    choose { %digits, map { $_ => 0 } ( $s, $e, $n, $d, $m, $o, $r ) }, sub { my $y = $_[0];
        my $send = $s . $e . $n . $d;
        my $more = $m . $o . $r . $e;
        my $money = $m . $o . $n . $e . $y;
        guard( ($send + $more == $money), sub {
            printf("%d + %d = %d\n", $send, $more, $money);
        });
    }}}}}}}};