4 &CAPS => subdir_CAPS _ counts
5 &lc => subdir/lc _ counts
7 &,= &,_ &,/ &,CAPS &,lc prefixes $(top_srcdir)/subdir
8 &;= &;_ &;/ &;CAPS &;lc prefixes $(abs_top_srcdir)/subdir
11 &: => $(abs_top_srcdir)
13 & thing thing => like &thing &thing (until EOL)
14 (edits only `thing's which are CAPS or lc
19 &! spc disables & *until* EOL
21 &!STUFF STUFF is recognised instead of & (beyond EOL)
22 STUFF is either all punct or all alphanum (incl _)
23 any lwsp after STUFF is discarded too
25 STUFF!& now & is recognised instead (ie back to normal)
29 &!@@@ @@@ is recognised instead of &
32 &TARGETS[_things] is handled specially
33 must be spelled precisely this way
34 if no _things, means _all