$output_file = 'output_file';

backup_the_data(\$output_file);

sub backup_the_data {
   my ($file) = @_;

   my $filesize = 0;
   # my $filesize = -s $$file;
   $filesize = -s $$file;

   if ($filesize != 0){ 
      copy($$file, $$file . '_backup');
   }
}