Reg exp perl code#

The hash character # is not available as a delimiter since it is parsed as the start of a comment that runs until the end of the line. Use of a colon as a delimiter would clash with the use of adverbs, which take the form :adverb accordingly, such use of the colon is forbidden. The form rx ( abc ), however, does define a Regex object. For example, in rx() the call operator () invokes the subroutine rx. This is because identifiers that are immediately followed by parentheses are always parsed as a subroutine call. Parentheses can be used as alternative regex delimiters, but only with a space between rx and the opening delimiter. Whitespace in regex definition syntax is generally optional, except where it is required to distinguish from function call syntax (discussed hereafter). You cannot use whitespace or alphanumeric characters as delimiters. * / # definition somewhat easier on the eyes than the secondĪlthough the choice is vast, not every character may be chosen as an alternative regex delimiter: Anonymous regex definition syntaxĪn anonymous regex may be constructed in one of the following ways: Yet, the syntax for constructing anonymous and named Regex objects differs.

Reg exp perl code#

Lexical conventionsįundamentally, Raku regexes are very much like subroutines: both are code objects, and just as you can have anonymous subs and named subs, you can have anonymous and named regexes.Ī regex, whether anonymous or named, is represented by a Regex object. This page describes this language, and explains how regexes can be used to search for text patterns in strings in a process called pattern matching. In Raku, regexes are written in a domain-specific language, i.e. In acknowledgement of this, and in an attempt to disambiguate, a regular expression in Raku is normally referred to as a regex (from: regular expression), a term that is also in common use in other programming languages. Since their inception in the 1950's, practical implementations of regular expressions, for instance in the text search and replace functions of text editors, have outgrown their strict scientific definition. In theoretical computer science and formal language theory, regular expressions are used to describe so-called regular languages. $/ changes each time a regular expression is matchedĪ regular expression is a sequence of characters that defines a certain text pattern, typically one that one wishes to find in some large body of text.

Regex readability: whitespace and comments Pattern matching against strings Table of Contents 1