Which statement about Perl regular expressions is true?

Perl regular expressions are indeed characterized by the inclusion of metacharacters, which are special characters that provide additional functionality beyond basic character matching. Metacharacters allow for sophisticated pattern matching in strings, such as specifying character classes, quantifiers, anchors, grouping, and alternation. This range of features makes them extremely powerful for text processing and searching.

The inclusion of metacharacters is a hallmark of Perl regular expressions, enabling users to construct complex search patterns effectively. This is particularly important in SAS, where such regular expressions can be employed within various procedures and data step functions to validate and manipulate strings.

The other choices present misunderstandings about the functionality of Perl regular expressions. They are not limited by a specific byte size, can indeed be utilized within SAS programming, and do not adhere to a single syntax since the Perl regular expression syntax allows for versatility and various extensions that offer numerous features for string manipulation.