grep с регулярными выражениями, совместимыми с Perl (a grep with Perl-compatible regular expressions.)
Переменные окружения (Environment variables)
The environment variables LC_ALL and LC_CTYPE are examined, in
that order, for a locale. The first one that is set is used. This
can be overridden by the --locale option. If no locale is set,
the PCRE library's default (usually the "C" locale) is used.
