use Data::Dumper;
open (my $infile, "<", "Input.txt") || die $!;

while (defined(my $line = <$infile>)) {
    chomp $line;
    my @rxn = split /#/, $line;
    next if length $rxn[1] == 0;
    my ($left_side, $right_side) = split /\s*<=>\s*/, $rxn[1], 2;
    my @left_elements = split /\s*\+\s*/, $left_side;
    my @right_elements = split /\s*\+\s*/, $right_side;

    my @combinations;
    for my $left_element (@left_elements) {
        for my $right_element (@right_elements) {
            push @combinations,  [$left_element, $right_element];
        }
    }
    print join(", ", map { "$_->[0]=$_->[1]" } @combinations), "\n";
    # print Dumper(\@combinations);
}