Oh, but dmorgo, you can do a simple UNIX-like paste. First construct a paste subroutine similar to the one below:

sub paste {
    my @fh = @_;
    return sub {
        chomp( my @line = map { scalar(<$_>) } @fh );
        return join ' ', @line;
    }
}
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Notice that this sub returns another anonymous sub (called an iterator) that reads one line at a time from each of the input file handles and returns them "pasted" together, separated only by a little whitespace for easy splitting. To take advantage of this code, simply open your files and paste them together.

open my $keys, "keys.txt" or die "couldn't open keys.txt";
open my $vals, "vals.txt" or die "couldn't open vals.txt";
my $combined = paste($keys,$vals);
print $combined->(), "\n" for 0..4;
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Using the example keys and vals given in your question, the output of this reads:

Joe 5
Bob 3
Sally 7
Bob 1
Fred 1
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If the deref syntax of $combined->() isn't quite to your taste, then whip up a little syntactic sugar to help the medicine go down:

sub NEXTLINE { $_[0]->() }
print NEXTLINE($combined), "\n" for 0..4;
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There are two benefits to this method that I can think of immediately. One is that it allows you to use a sub similar to the UNIX paste command with which you are already familiar. The second is that it avoids both the generation of a potentially huge %combined hash and the generation of a potentially huge combined.txt file. The concept of an iterator is not my original idea, but I use it whenever possible to keep my code clean and orderly. See Mark Jason Dominus's excellent text Higher Order Perl for more tricks and details on iterators.