Regexp Conditional Error Messages

QUERY: SELECT 1 REGEXP ''
ERROR: Got error 'empty (sub)expression' FROM REGEXP

QUERY: SELECT 1 REGEXP '('
ERROR: Got error 'parentheses not balanced' FROM REGEXP

QUERY: SELECT 1 REGEXP '['
ERROR: Got error 'brackets ([ ]) not balanced' FROM REGEXP

QUERY: SELECT 1 REGEXP '\\'
ERROR: Got error 'trailing backslash (\)' FROM REGEXP

QUERY: SELECT 1 REGEXP '*'
ERROR: Got error 'repetition-operator operand invalid' FROM REGEXP

QUERY: SELECT 1 REGEXP 'a{1,1,1}'
ERROR: Got error 'invalid repetition count(s)' FROM REGEXP

QUERY: SELECT 1 REGEXP '[a-9]'
ERROR: Got error 'invalid character range' FROM REGEXP

QUERY: SELECT 1 REGEXP 'a{1,'
ERROR: Got error 'braces not balanced' FROM REGEXP

QUERY: SELECT 1 REGEXP '[[.ab.]]'
ERROR: Got error 'invalid collating element' FROM REGEXP

QUERY: SELECT 1 REGEXP '[[:ab:]]'
ERROR: Got error 'invalid character class' FROM REGEXP