Perl 6 Deep Dive

Character class arithmetics

Perl 6 offers great power, allowing you to create new character classes using operations over sets. These are—+ or | for union, - for difference, & for intersection, and ^ for the XOR operation. Additionally, character classes can be negated with either - or !.

Let us look at examples. First, create the joined class that matches with both lowercase letters and digits:

for <a A 3> -> $char {    say "$char is a lowercase letter or a digit"         if $char ~~ / <:Ll + :Nd> /;}

This program print matches for the characters a and 3. The capital A does not match because it is neither a lowercase letter nor a digit.

In another example, we reinvent uppercase letters by subtracting lowercase letters from the set of all letters: ...