Try this regex(.,[A-Z]+) Match a single character present in the list below [A-Z]+
- Quantifier — Matches between one and unlimited times, as many times as possible.
Another alternative I am using now is instead to prevent lowercase in input, just to normalize to UPPERCASE using XPATH translate. The translate() function enables such things converting strings from lowercase to uppercase, by translate(${mystring}, 'abcde...', 'ABCDE...').