&= => sub_dir or TOP
-&^lc => $(top_srcdir)/sub/dir/lc
-&^/ => $(top_srcdir)/sub/dir/
-&^. => $(top_srcdir)/sub/dir
+&^lc => ${top_srcdir}/sub/dir/lc
+&^/ => ${top_srcdir}/sub/dir/
+&^. => ${top_srcdir}/sub/dir
-&~lc => $(top_srcdir)/lc
-&~/ => $(top_srcdir)/
-&~. => $(top_srcdir)
+&~lc => ${top_srcdir}/lc
+&~/ => ${top_srcdir}/
+&~. => ${top_srcdir}
In general:
^ pathname of this subdirectory in source tree