#!/usr/bin/perl -w

use strict;
use warnings;

$|=1;

sub multiply {
    my( $ref1, $ref2 ) = @_;
    my @temp;
    for my $r1 ( @{ $ref1 } ) {
        for my $r2 ( @{ $ref2 } ) {
            push @temp, $r2 . $r1;
        }
    }
    return \@temp;
}

$/ = ',';
my @stack;

open POSTFIX, '<', 'postfix.txt' or die $!;

while( my $op = <POSTFIX> ) {
    chomp $op;
    $op =~ tr/\r\n//d; ## remove any trailing newline

    if( $op eq 'x' ) {
	print STDERR "MULTIPLY\n";
        push @stack, multiply( pop( @stack ), pop( @stack ) );
    }
    elsif( $op eq '+' ) {
	print STDERR "ADD\n";
        push @stack, [ @{ pop @stack }, @{ pop @stack } ];
    }
    elsif( $op =~ m[^\d+$] ) {
        push @stack, [ pack 'v', $op ];
    }
    else {
        die "Bad '$op' at position;" . tell( POSTFIX );
    }
}

print STDERR "stacksize: " . @stack. "\n";

for my $item ( @stack ) {
    printf "%s", join ',', unpack 'v*', @{ $item }[ 0 ];
    for my $group ( @{ $item }[ 1 .. $#$item ] ) {
        printf "+%s", join ',', unpack 'v*', $group;
    }
    print "\n";
}