The string position/offset cache is not optional. It should be.
+=head2 Unicode in Filenames
+
+chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open,
+opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen,
+system, truncate, unlink, utime, -X. All these could potentially accept
+Unicode filenames either as input or output (and in the case of system
+and qx Unicode in general, as input or output to/from the shell).
+Whether a filesystem - an operating system pair understands Unicode in
+filenames varies.
+
+Known combinations that have some level of understanding include
+Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac
+OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to
+create Unicode filenames, what forms of Unicode are accepted and used
+(UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used,
+and so on, varies. Finding the right level of interfacing to Perl
+requires some thought. Remember that an OS does not implicate a
+filesystem.
+
+(The Windows -C command flag "wide API support" has been at least
+temporarily retired in 5.8.1, and the -C has been repurposed, see
+L<perlrun>.)
+
+=head2 Unicode in %ENV
+
+Currently the %ENV entries are always byte strings.
+
=head1 Regexps
=head2 regexp optimiser optional
The regexp optimiser is not optional. It should configurable to be, to allow
its performance to be measured, and its bugs to be easily demonstrated.
-=head2 common suffices/prefixes in regexps (trie optimization)
+=head2 common suffices/prefices in regexps (trie optimization)
Currently, the user has to optimize C<foo|far> and C<foo|goo> into
C<f(?:oo|ar)> and C<[fg]oo> by hand; this could be done automatically.
=head2 POD -> HTML conversion still sucks
+Which is crazy given just how simple POD purports to be, and how simple HTML
+can be.
+
=head1 Misc medium sized projects
=head2 UNITCHECK