This is straight from the examples section of the CGI.pm documentation:

# Process the form if there is a file name entered
if (my $file = param('filename')) {
    my %stats;
    my $tmpfile=tmpFileName($file);
    my $mimetype = uploadInfo($file)->{'Content-Type'} || '';
    print hr(),
          h2($file),
          h3($tmpfile),
          h4("MIME Type:",em($mimetype));

    my($lines,$words,$characters,@words) = (0,0,0,0);
    while (<$file>) {
        $lines++;
        $words += @words=split(/\s+/);
        $characters += length($_);
    }
    close $file;
    grep($stats{$_}++,param('count'));
    if (%stats) {
        print strong("Lines: "),$lines,br if $stats{'count lines'};
        print strong("Words: "),$words,br if $stats{'count words'};
        print strong("Characters: "),$characters,br if $stats{'count c
+haracters'};
    } else {
        print strong("No statistics selected.");
    }
}
[download]

Of course, this is for processing a text file. To get information from an uploaded binary file, I do a stat() on the filehandle.

 $filename = $query->param('uploaded_file');
 @stats=stat $filename;
 $size_of_file=$stats[7];
[download]

Hope this helps!
Oakbox
"If what I'm saying doesn't make sense, that's because sense cannot be made, it's something that must be sensed"-J.S. Hall