Handle Slackware 14.2 in a cleaner way via pkgsrc

Didn't like the hack I was using to work around an old perl before. So
when I noticed that using pkgsrc in Slackware pretty soon puts down a
recent perl as a dependency to many things I decided that using that
would be better than overlaying a newer List::Util version on perl 5.22.

This change detects the newest perl on the system at install time and
puts that in the script interpreter line. It removes the wrapper that
included a library tree with new versions of core Perl modules.

Makefile

@@ -1,15 +1,16 @@
-check:
-	perl -wc frfac
-	perlcritic frfac
+frfac:
+	sed "1d;2i #!`./latest_perl`" frfac.in > frfac
 
-install:
+check:
+	`./latest_perl` -wc frfac.in
+	perlcritic frfac.in
+
+install: frfac
 	install -o root -g wheel -m 0755 -d /usr/local/bin
 	install -o root -g wheel -m 0555 frfac /usr/local/bin
 
-install_with_newcore_hack:
-	install -o root -g wheel -m 0755 -d /usr/local/bin
-	install -o root -g wheel -m 0555 frfac /usr/local/share/perl5/
-	install -o root -g wheel -m 0555 frfac.wrapper /usr/local/bin/frfac
+clean:
+	rm -f frfac
 
 uninstall:
-	rm -f /usr/local/bin/frfac /usr/local/share/perl5/frfac
+	rm -f /usr/local/bin/frfac