phpman > perldoc > locale(5)

NAME
    locale - Perl pragma to use or avoid POSIX locales for built-in operations

WARNING
    DO NOT USE this pragma in scripts that have multiple threads active. The locale is not local to
    a single thread. Another thread may change the locale at any time, which could cause at a
    minimum that a given thread is operating in a locale it isn't expecting to be in. On some
    platforms, segfaults can also occur. The locale change need not be explicit; some operations
    cause perl to change the locale itself. You are vulnerable simply by having done a ""use
    locale"".

SYNOPSIS
        @x = sort @y;      # Native-platform/Unicode code point sort order
        {
            use locale;
            @x = sort @y;  # Locale-defined sort order
        }
        @x = sort @y;      # Native-platform/Unicode code point sort order
                           # again

DESCRIPTION
    This pragma tells the compiler to enable (or disable) the use of POSIX locales for built-in
    operations (for example, LC_CTYPE for regular expressions, LC_COLLATE for string comparison, and
    LC_NUMERIC for number formatting). 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.

    On systems that don't have locales, this pragma will cause your operations to behave as if in
    the "C" locale; attempts to change the locale will fail.