You want to classify values into broad categories.
Solution
Use a pattern that is similarly broad.
Discussion
If you need to know whether values are empty or nonempty, or
consist only of certain types of characters, the patterns listed in
the following table may suffice:
Pattern
Type of value the pattern matches
/^$/
Empty value
/./
Nonempty value
/^s*$/
Whitespace, possibly
empty
/^s+$/
Nonempty
whitespace
/S/
Nonempty, and not just
whitespace
/^d+$/
Digits only,
nonempty
/^[a-z]+$/i
Alphabetic characters only
(case-insensitive), nonempty
/^w+$/
Alphanumeric or underscore
characters only, nonempty