Is this what you want?

sub mailme {
   my ($to, $sub, $file_path) = @_;

   my $msg = MIME::Lite->new(
      From    => 'MAILER-DAEMON root',
      To      => $to,
      Subject => $sub,
      Type    => 'multipart/related',
   );

   $msg->attach(
      Type => 'TEXT',
      Data => "See attachment!",
   );

   $msg->attach(
      Type        => 'TEXT',
      Disposition => 'attachment',
      Path        => $file_path,
   );

   $msg->send;
}

mailme('operations@xxxx.com', $sub, $log);
[download]

• Added desired parameter.
• Arranged order of arguments more logically.
• Combined the three fetches from @_ into one statement.
• Fixed indentation.
• Removed useless stringification ("$foo" ⇒ $foo).
• Removed useless Filename argument (which wasn't even a file name).