Changed perl into macro to allow command-line override to non-syste…

…m perl

Makefile

@@ -10,6 +10,8 @@ CHAPTERS =src/preface.pod \
 		  src/grammars.pod \
 		  src/builtins.pod
 
+PERL = perl
+
 # If you're on a Mac, and installed Inkscape via MacPorts, you might want to
 # manually uncomment the next line, and remove the one after it.
 #INKSCAPE = /Applications/Inkscape.app/Contents/Resources/bin/inkscape
@@ -24,13 +26,13 @@ build/mmd-table.pdf: src/mmd-table.svg
 	$(INKSCAPE) --export-pdf=build/mmd-table.pdf -D src/mmd-table.svg
 
 build/book.html: $(CHAPTERS) bin/book-to-html
-	perl bin/book-to-html $(CHAPTERS) > build/book.html
+	$(PERL) bin/book-to-html $(CHAPTERS) > build/book.html
 
 build/book.pdf:	build/book.tex build/mmd-table.pdf
 	cd build && pdflatex book.tex && makeindex book && pdflatex book.tex
 
 build/book.tex: $(CHAPTERS) bin/book-to-latex
-	perl bin/book-to-latex $(CHAPTERS) > build/book.tex
+	$(PERL) bin/book-to-latex $(CHAPTERS) > build/book.tex
 
 clean: 
 	rm -rf build/*