Farrago probably does not have 'Regular character set identifiers' like :ALPHA: , :UPPER: , :LOWER: , :ALNUM: , :SPACE: , :WHITESPACE: , :DIGIT: etc defined or supported in SIMILAR TO predicates.

e.g. all queries below return false.

VALUES('yd32' SIMILAR TO [:LOWER:]{2}[:DIGIT:]*');
VALUES('yd32' SIMILAR TO '[:ALNUM:]*');
VALUES('yd32' SIMILAR TO '[:ALNUM:]*[:DIGIT:]?');
VALUES('yd32' SIMILAR TO '[:ALNUM:]?[:DIGIT:]*');
VALUES('yd3223' SIMILAR TO '[:LOWER:]{2}[:DIGIT:]{,5}'); -- supposed to fail as illegal regex.
VALUES('yd3223' SIMILAR TO '([:LOWER:]{2})[:DIGIT:]{2,5}');
VALUES('yd3223' SIMILAR TO '[:LOWER:]{2}[:DIGIT:]{2,}');
VALUES('yd3223' SIMILAR TO '[:LOWER:]{2}||[:DIGIT:]{4}');
VALUES('yd3223' SIMILAR TO '[:LOWER:]{2}[:DIGIT:]{3}');
VALUES('yd 3223' SIMILAR TO '[:UPPER:]{2} [:DIGIT:]{3}');
VALUES('YD 3223' SIMILAR TO '[:UPPER:]{2} [:DIGIT:]{3}');
VALUES('YD 3223' SIMILAR TO '[:UPPER:]{2}||[:WHITESPACE:]*[:DIGIT:]{3}');