Well, you don't simply swap return for print, because as you've discovered, return exits a subroutine (see perlintro)

The CGI::Application documentation shows you the correct way to do it

...
my $output = "";
foreach my $row ( @$Results ) {
  $output .= "$row->{'DOC_SUB_TYPE'}|$row->{'DESCRIPTION'}\n";
}
return $output;
...
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