RegExp to find pos in str of invalid chars

Good morning.

I would like to use one or more RegExps to validate country names as having
the first and last words beginning with an uppercase letter, intermediate
words beginning with either uppercase or lowercase, and all other characters
being lowercase characters. For example:

Turks and Caicos

The difficult part is that I want to obtain save the string positions of the
invalid characters in an array, rather than just obtain a true or false
value.

Can anybody with more experience with Regular Expressions than me suggest
some code, sites, or approaches.

Thanks,
Ron