use vars qw[$dbuser $dbpass $dbsecret_time];

my $secretfile = '/path/db.txt';
my $secretfile_modtime = stat($secretfile)[9];
if (!$dbsecret_time or $dbsecret_time < $secretfile_modtime)
{
  open FILE, '<', $file or die $!;
  chomp(my ($auth) =  <FILE>);
  ($dbuser, $dbpasswd) = split('\t', $auth);
  close FILE;
  $dbsecret_time = $secretfile_modtime;
}