There is no AND operator in this version of regular expressions. You may have one or more characters in this set. Regular expressions are case-sensitive. The pattern 'AAAA' will not match the sequence 'aaaa'. Here is a sample session with preg.
Regular expressions are case-sensitive.
The pattern 'AAAA' will not match the sequence 'aaaa'. Diagnostic Error Messages Exit status Always returns 0. This program is intended to be used by everyone and everything, from naive users to embedded scripts.