Thanks roboticus. I have modified my function and now I'm able to get both body message as well as attachment in mail. Function Code:

sub sendmailto {
             $mailing_list = $_[0];
             $subject = $_[1];
             $message = $_[2];
             $from = "naga.rajan@gmail.com"
             $attachment = `uuencode "/home/naga/testing-scripts/Packa
+ge_Specification_Document.doc" "Package_Specification_Document.doc"
        open (MAIL, "|mailx -s "$subject\" -r $from $mailing_list");
        print MAIL "Hi, \n";
        print MAIL "\n";
        print MAIL "This email was sent using an automated email syste
+m. Please do not reply, or forward to this email otherwise your messa
+ge will not reach your intended recipients. \n";
        print MAIL "If you like to contact us pleas write to *UNIX Tea
+m. \n";
        print MAIL "\n";
        print MAIL "Regards, \n";
        print MAIL "UNIX Team \n";
        print MAIL "\n";
        print MAIL "\n";
        print MAIL "$message";
        print MAIL $attachment;
close MAIL;
}
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If I paste  print MAIL $attachment; next to mailx  open (MAIL, "|mailx -s "$subject\" -r $from $mailing_list"); then body content is getting missed. If we paste before closing MAIL file handler then we are able to get both body message as well as attachment in mail.