hm
you could do this:

my(%file_a);
open(FILEA,"path_to_file_a");
open(FILEB,"path_to_file_b");

while(my $line = <FILEA>){
   chomp($line);
   my @values = split /|/, $line;
   $file_a{$values[0]}=$values[1];
}
close(FILEA);
my ($calc_prod,$total);
while(my $line = <FILEB>) {
    chomp($line);
    if($line =~ m/^Group Name/) {
        print "Total: $total\n" if $total > 0;
        print "Group ", {$line =~ m/^Group Name: (.*)$/}, "\n";
        $calc_prod = 0;
        $total = 0;
    }
    next if $line =~ m/^Junk/;
    if($line =~ m/^Product Name/) {
        $calc_prod = 1; next;
    }
    if ($calc_prod) {
        print "$line ",$file_a{$line};
        $total += $file_a{$line};
    }
}
close(FILEB);
[download]

I wrote this without checking the syntax, but you'll see what we're trying to do ;-)