C:\>perl -le "my $str = qq(foo\x{100}bar); my $re = qr/^\Q$str\E/; warn $str; warn $re; warn $str =~
 /$re/;"
foo─Çbar at -e line 1.
(?-xism:^foo─Çbar) at -e line 1.
1 at -e line 1.