Tie Modules
	VecArray		Implement array using vec()
	SubstrArray		Implement array using substr()
	VirtualArray		Implement array using a file
	ShiftSplice		Defines shift et al in terms of splice method

Would be nice to have
	pack "(stuff)*"
	Contiguous bitfields in pack/unpack
	lexperl
	Bundled perl preprocessor
	Use posix calls internally where possible
	gettimeofday (possibly best left for a module?)
	format BOTTOM
	-i rename file only when successfully changed
	All ARGV input should act like <>
	report HANDLE [formats].
	support in perlmain to rerun debugger
	regression tests using __DIE__ hook
	reference to compiled regexp
	lexically scoped functions: my sub foo { ... }
	lvalue functions
	regression/sanity tests for suidperl
	Full 64 bit support (i.e. "long long")
	Generalise Errno way of extracting cpp symbols and use that in
	    Errno and Fcntl (ExtUtils::CppSymbol?)

Possible pragmas
	debugger
	optimize (use less memory, CPU)

Optimizations
	constant function cache
	switch structures
	foreach(reverse...)
	Set KEEP on constant split
	Cache eval tree (unless lexical outer scope used (mark in &compiling?))
	rcatmaybe
	Shrink opcode tables via multiple implementations selected in peep
	Cache hash value?  (Not a win, according to Guido)
	Optimize away @_ where possible
	"one pass" global destruction
	Rewrite regexp parser for better integrated optimization
	LRU cache of regexp: foreach $pat (@pats) { foo() if /$pat/ }

Vague possibilities
	ref function in list context
	make tr/// return histogram in list context?
	Loop control on do{} et al
	Explicit switch statements
	built-in globbing
	compile to real threaded code
	structured types
	autocroak?
	Modifiable $1 et al