Sub-patterns can be wrapped by parentheses to build a group. This enables to restrict alternations, back reference the group or apply quantifier to the sub-pattern.

If this group should not be part of the match result or if no reference to this group is required, a non-capturing group can be created by adding `?:` behind the opening parenthesis.

However, if this non-capturing group does not have a quantifier, or does not wrap an alternation, then imaging this group is redundant.
