Perl 5 version 8.9 documentation
locale - Perl pragma to use and avoid POSIX locales for built-in operations
This pragma tells the compiler to enable (or disable) the use of POSIX locales for built-in operations (LC_CTYPE for regular expressions, and LC_COLLATE for string comparison). Each "use locale" or "no locale" affects statements to the end of the enclosing BLOCK.
See perllocale for more detailed information on how Perl supports locales.