Unicode::Regex::Set 0.02

Unicode::Regex::Set is a subtraction and intersection of Character Sets in Unicode Regular Expressions.

SYNOPSIS

use Unicode::Regex::Set qw(parse);

$regex = parse([p{Latin} & p{L&} - A-Z]);

Perl 5.8.0 misses subtraction and intersection of characters, which is described in Unicode Regular Expressions (UTS #18). This module provides a mimic syntax of character classes including subtraction and intersection, taking advantage of look-ahead assertions.

The syntax provided by this module is considerably incompatible with the standard Perls regex syntax.

Any whitespace character (that matches /s/) is allowed between any tokens. Square brackets ([ and ]) are used for grouping. A literal whitespace and square brackets must be backslashed (escaped with a backslash, ). You cannot put literal ] at the start of a group.

A POSIX-style character class like [:alpha:] is allowed since its [ is not a literal.
SEPARATORS (& for intersection, | for union, and - for subtraction) should be enclosed with one or more whitespaces. E.g. [A&Z] is a list of A, &, Z. [A-Z] is a character range from A to Z. [A-Z - Z] is a set by removal of [Z] from [A-Z].
Union operator | may be omitted. E.g. [A-Z | a-z] is equivalent to [A-Z a-z], and also to [A-Za-z].

Intersection operator & has high precedence, so [p{A} p{B} & p{C} p{D}] is equivalent to [p{A} | [p{B} & p{C}] | p{D}].

Subtraction operator - has low precedence, so [p{A} p{B} - p{C} p{D}] is equivalent to [[p{A} | p{B}] - [p{C} | p{D}] ].

[p{A} - p{B} - p{C}] is a set by removal of p{B} and p{C} from p{A}. It is equivalent to [p{A} - [p{B} p{C}]] and [p{A} - p{B} p{C}].

Negation. when ^ just after a group-opening [, i.e. when they are combined as [^, all the tokens following are negated. E.g. [^A-Z a-z] matches anything but neither [A-Z] nor [a-z]. More clearly you can say this with grouping as [^ [A-Z a-z]].

If ^ that is not next to [ is prefixed to a sequence of literal characters, character ranges, and/or metacharacters, such a ^ only negates that sequence; e.g. [A-Z ^p{Latin}] matches A-Z or a non-Latin character. But [A-Z [^p{Latin}]] (or [A-Z P{Latin}], for this is a simple case) is recommended for clarity.

If you want to remove anything other than PERL from [A-Z], use [A-Z & PERL] as well as [A-Z - [^PERL]]. Similarly, if you want to intersect [A-Z] and a thing not JUNK, use [A-Z - JUNK] as well as [A-Z & [^JUNK]].