One of the most important features of regular expressions is the ability to store a part of a matched pattern for later reuse. As you'll recall, placing parentheses around a regular expression pattern or part of a pattern causes that part of the expression to be stored into a temporary buffer. You can override the saving of that part of the regular expression using the non-capturing metacharacters '?:', '?=', or '?!'.

Expand imageStoring Submatches