You are viewing the version of this documentation from Perl 5.31.5. This is a development release of Perl.
${^UTF8LOCALE}

This variable indicates whether a UTF-8 locale was detected by perl at startup. This information is used by perl when it's in adjust-utf8ness-to-locale mode (as when run with the -CL command-line switch); see perlrun for more info on this.

This variable was added in Perl v5.8.8.