I usualy use POSIX::tmpnam for this. It returns a still available file name for the /tmp dir. (eg: /tmp/fileErjARC). example code:

use POSIX qw(tmpnam);
use strict; # || loose XP.
use Sender; # ?

my $tmpfile = tmpnam();
open(OUT, ">$tmpfile") || die("Can't write tmp-file");
print OUT "data ... data ... data\n";
close(OUT);

my $sender = Sender new;

## create message with attachment
  $sender->MailFile({
        to              => "$username\@mycompany.inc",
        subject         => "$subject",
        msg             => "Attached is the info you need!", 
        file            => "$tmpfile",
  });

unlink $tmpfile;
[download]

I guess this is what you meant?

Sinister greetings.
"With tying hashes you can do everything God and Larry have forbidden" -- Johan Vromans - YAPC::Europe 2001
perldoc -q $_