sub validate_password {
  my ($field,$pass) = @_ ;
  my $minlen = 5 ;
  return "Field $field: Password too short (min. $minlen chars)"
    if length($pass) < $minlen ;
  return "Field $field: Please use alphabetics and digits (at least)"
    unless $pass =~ /[a-z/i and $pass =~ /\d/ ;
...