... what i tried was actually:

elsif ( $data eq "8000" || "0080" ) {
     $tid = .....;
}
[download]

As you discovered, this syntax doesn't work — at least, not the way you expected: the truth value of the expression  $data eq '8000' is logical-ored with '8000'. Again, let Perl help you:

c:\@Work\Perl\monks>perl -wMstrict -MO=Deparse,-p -le
"my $data = '8000';
 ;;
 if ($data eq '8000' || '0080') { print 'yes'; };
"
BEGIN { $^W = 1; }
BEGIN { $/ = "\n"; $\ = "\n"; }
use strict 'refs';
(my $data = '8000');
if ((($data eq '8000') or '0080')) {
    print('yes');
}
-e syntax OK
[download]