Programming Perl, 4th Edition

Character Properties

Character properties are available using \p{PROP} and its set complement, \P{PROP}. For the seven major Unicode General Category properties of just one letter, the braces on the \p and \P are optional. So you may write \pL for any letter or \pN for any number, but you must use braces for anything longer, like \p{Lm} or \p{Nl}.

Most properties are directly defined in the Unicode Standard, but some, usually composites built out of the standard properties, are peculiar to Perl. For example Nl and Mn are standard Unicode General Categories representing letter-numbers and nonspacing combining marks, while Perl_Space is of Perl’s own devising.

Properties may be used by themselves or combined in a constructed character class:

if ($var =~ /^\p{alpha}+$/)   { say "all alphabetic" }
if ($var =~ s/[^\pL\pN]//g)   { say "deleted all nonalphanumerics" }

There are a great many properties, and some of those commonly used ones each cover more characters than many people imagine. For example, the alpha and word properties each cover over 100,000 characters, with word necessarily being the larger of the two as it is a proper superset of alpha.

The current list of properties supported by your release of Perl can be found in the perluniprops manpage, including how many characters each property matches. Perl closely tracks the Unicode Standard, so as new properties are added to Unicode, they are also added to Perl. For official Unicode properties, see UAX #44: Unicode Character Database, ...