Apparently FreeBSD's make lacks +!= operator, so work it around. Also detect perl executable and allow overriding name for -ltidy because FreeBSD apparently overrides it.
I don't really know all the intricacies of BSD make but all of this
seems reasonable to me. Will merge in the next day or so after I've had
a chance to give it a second look.
Apparently FreeBSD's make lacks
+!=
operator, so work it around. Also detectperl
executable and allow overriding name for-ltidy
because FreeBSD apparently overrides it.