Regex
3.4.2 The Match-one-or-more Operator (+ or \+)
If the syntax bit RE_LIMITED_OPS is set, then Regex doesn't recognize
this operator. Otherwise, if the syntax bit RE_BK_PLUS_QM isn't
set, then `+' represents this operator; if it is, then `\+'
does.
This operator is similar to the match-zero-or-more operator except that
it repeats the preceding regular expression at least once;
see section 3.4.1 The Match-zero-or-more Operator (*), for what it operates on, how some
syntax bits affect it, and how Regex backtracks to match it.
For example, supposing that `+' represents the match-one-or-more
operator; then `ca+r' matches, e.g., `car' and
`caaaar', but not `cr'.
