native_is_utf8

Return true if the scalar carries the SVf_UTF8 flag.

Synopsis

my $flagged = is_utf8($string);
my $flagged = is_utf8($string, $check);

With one argument, is_utf8 reports the flag as-is. With a true $check, the bytes are also validated as UTF-8; a flagged scalar whose bytes are not valid UTF-8 returns false.

This is a low-level diagnostic. Regular Perl code should not need it — the flag is an internal implementation detail, and the right place to think about “is this text” is at I/O boundaries with encode/decode.

Differences from upstream

Fully compatible with upstream. Covered by t/81-xs-native/Encode/080-utf8-flags.t.