Cause: In previous versions, the 'gawk' utility was using the POSIX definition as default, when searching for a range patterns of given regular expression. For example, if you used regular expression '[A-Z]', it also matched lowercase symbols of alphabet.
Consequence: This behaviour was not intuitive and was confusing to many users of 'gawk'
Fix: Upstream of the 'gawk' has already introduced patches to change it to the more intuitive behaviour. We have backported all the related changed to the current version of the 'gawk' utility.
Result: After the fix, the 'gawk' utility's regular expressions match only uppercase characters when '[A-Z]' is used. However, the previous behaviour can be still enabled if needed, by using the '--posix' parameter of the 'gawk'.