NOTES

   1 &CAPS           =>      subdir_CAPS                     or TOP_CAPS
   2 &lc             =>      subdir/lc                       or lc
   3
   4 &_              =>      subdir_                         or TOP_
   5 &/              =>      subdir/                         or nothing
   6 &=_             =>      subdir                          or TOP
   7 &=/             =>      subdir                          or .
   8 &^              =>      $(top_srcdir)/subdir            or $(top_srcdir)
   9 &~              =>      $(abs_top_srcdir)/subdir        or $(abs_top_srcdir)
  10
  11 &&                      =>      &
  12
  13 & thing thing... &      =>      each thing prefixed by &/ &^ &~ resp
  14 & ^ thing thing... &            each thing is any non-ws
  15 & ~ thing thing... &            & may be omitted before EOL or before \EOL
  16
  17 CAPS is [A-Z][0-9_A-Z]*(?!\w)
  18 lc is [a-z][-+,0-9_a-z]*(?!\w)
  19
  20 &! spc          disables & *until* EOL
  21
  22 &!STUFF         STUFF is recognised instead of & (beyond EOL)
  23                 STUFF is either all punct or all alphanum (incl _)
  24                 any lwsp after STUFF is discarded too
  25 eg notably
  26  STUFF!&                now & is recognised instead (ie back to normal)
  27  STUFFSTUFF     STUFF
  28
  29 eg
  30  &!@@@          @@@ is recognised instead of &
  31  @@@!&          go back to &
  32
  33 &TARGETS[_things]               is handled specially
  34                                 must be spelled precisely this way
  35                                 if no _things, means _all
  36
  37 Also, `all' is weird in that it is present even if not specified