Checking for diacritics with a regular expression
Solution 1:
You can use the specific Unicode escape for letters - \p{L} (this will include the A-Za-z ranges):
^[.\p{L}]*$
See on regularexpressions.info:
\p{L} or \p{Letter}
Matches a single Unicode code point that has the property "letter". See Unicode Character Properties in the tutorial for a complete list of properties. Each Unicode code point has exactly one property. Can be used inside character classes.