sub paste {
    my @fh = @_;
    return sub {
        chomp( my @line = map { scalar(<$_>) } @fh );
        return join ' ', @line;
    }
}

##</code><code>##

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;

##</code><code>##

Joe 5
Bob 3
Sally 7
Bob 1
Fred 1

##</code><code>##

sub NEXTLINE { $_[0]->() }
print NEXTLINE($combined), "\n" for 0..4;