Good on ya. What have you tried though and were does it go wrong? I'd guess you might have tried using a hash and counted the number of entries then printed out the ones that were unique (have a count of 1), but it's not clear where you are having trouble.

And the question is?

So here 6.66 would be returned?

But you're not asking us to do your homework, are you? If not, as we all hope, what have you tried thus far? Which is your code?

Said this, it's not entirely clear to me whether you want uniq numbers per file or amongst all files. Whatever, you may have guessed that this kind of questions gets asked quite frequently, and indeed there's at least a faq that should be of considerable interest to you: check perldoc -q unique.

Also, you may have done a search here (or a Super Search); in particular a question with a subject nearly identical to yours has been asked quite recently.

use Fatal qw/open/;
my %h;
open my $fh, '<', '/tmp/file1';
while ( defined ($_ = <$fh>)){
  /^([\d.]+)/ and $h{$1}++;
}
open  $fh, '<', '/tmp/file2';
while ( defined ($_ = <$fh>)){
  /^([\d.]+)/ and delete $h{$1};
}
print join "\n", keys %h;
[download]

Consider:

file1
6.66 6.75
6.75 6.66
6.75 6.75
7.17 7.17
7.31 7.31
7.41 7.41

file2
6.75 6.66
6.75 6.75
7.17 7.17
7.31 7.31
7.41 7.41
6.62 6.75
[download]

which should generate:

6.62
6.66
[download]

---

Perl is Huffman encoded by design.

Upps, you are so right.

use Fatal qw/open/;
my ( %h, %g );
open my $fh, '<', '/tmp/file1';
while ( defined ($_ = <$fh>)){
  /^([\d\.]+)/ and $h{$1}++;
}

open  $fh, '<', '/tmp/file2';
while ( defined ($_ = <$fh>)){
  /^([\d\.]+)/ and $g{$1}++;
}

my @k = keys %h;
delete @h{keys %g};
delete @g{@k};

print join "\n",( keys %h, keys %g );
[download]

Boris

thanks for getting me started