1 &CAPS => subdir_CAPS or TOP_CAPS
5 &/ => subdir/ or nothing
8 &^ => $(top_srcdir)/subdir or $(top_srcdir)
9 &~ => $(abs_top_srcdir)/subdir or $(abs_top_srcdir)
14 & thing thing... & => each thing prefixed by &/ &^/ &~/ resp
15 & ^ thing thing... & each thing is any non-ws
16 & ~ thing thing... & & may be omitted before EOL or before \EOL
17 other &'s not recognised
19 CAPS is [A-Z][0-9_A-Z]*(?!\w)
20 lc is [a-z][-+,0-9_a-z]*(?!\w)
22 &!<spaces or tabs> disables & *until* EOL (and disappears)
24 &!STUFF<lwsp> STUFF is recognised instead of &
25 the terminating lwsp is discarded too
29 STUFF!& now & is recognised instead (ie back to normal)
33 &!@@@ @@@ is recognised instead of &
36 &TARGETS[_things] is handled specially
37 must be spelled precisely this way
38 if no _things, means _all
40 Also, `all' is weird in that it is present even if not specified