use File::Temp;
use File::Basename qw( basename );

use constant DEST_PATH     => '/path/to/destination/';
use constant TEMP_PATH     => '/tmp';
use constant TMP_TEMPLATE  => 'prog_name.XXXX';

my $temp_fh = File::Temp->new(
  DIR      => TEMP_PATH,
  TEMPLATE => TMP_TEMPLATE,
  UNLINK   => 0
);

print "Temporary file created: ", $temp_fh->filename, "\n";

END{

  my $new_filename = DEST_PATH . basename($temp_fh->filename) . '.html';

  rename $temp_fh->filename, $new_filename or do{
    $temp_fh->unlink_on_destroy;
    die $temp_fh->filename, " couldn't be renamed: $!\n",
        "It will be unlinked instead.";
  };

  print "Temp file was renamed to $new_filename\n";
}