What file are you trying to send? The file at $rptname? Because with your open line, you just wiped out the contents of $rptname. Whatever was in there before is now gone, so there's nothing to feed into mailx.

Do you need to create a file? You could do all of this in memory. Just create a scalar that contains your mail message. Then send it using one of the Mail:: modules. Mail::Mailer may do what you want:

    use Mail::Mailer;

    my $mailer = new Mail::Mailer 'sendmail';

    $mailer->open( {
        To => 'foo@bar.com',
        Subject => 'Report' } );

    ## Create report in scalar $report... then write it.
    print $mailer $report;
    $mailer->close;
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You can also use SMTP or mail to send your mail.