1 error message at the time, custom regexp check on field

[eluser]xwero[/eluser]
valid_email, alpha, alpha_numeric, alpha_dash, ... are all regex rules so if you want to add a new regex rule i suggest you put it in it's own method instead of creating a catch all regex method.

Fetching the first error is fetching the first error of the field you added first to the rules. In the current validation library there is no way to get the first error of a certain field.
In the new library, see SVN, it is possible because there the level 1 keys are the fieldnames.