lang/perl5 wrkdir reference to rm tool

[Taylor R Campbell <campbell+netbsd-tech-pkg%mumble.net@localhost>]

Several people have seen Perl fail to build because the installed
Config_heavy.pl has a wrkdir reference to the rm tool.  This happens
when the build system decides to regenerate Config_heavy.pl after
pkgsrc has patched it.  The problem seems to have been around for a
while:

http://mail-index.netbsd.org/tech-pkg/2011/05/22/msg007191.html

I banged my head on this last month when I hit the symptom, and lost
the energy to dig around any more in Perl's build system to find the
real source of the problem, but I found a workaround that seemed to
work for me, attached, which is just to do the substitution in
config.sh instead of lib/Config_heavy.pl.  I'm not going to touch
lang/perl5 myself, but if anyone else has the courage to do that,
perhaps you'd find this useful.

Index: lang/perl5/Makefile
===================================================================
RCS file: /cvsroot/pkgsrc/lang/perl5/Makefile,v
retrieving revision 1.192
diff -p -u -r1.192 Makefile
--- lang/perl5/Makefile 12 Dec 2012 10:13:47 -0000      1.192
+++ lang/perl5/Makefile 23 Dec 2012 17:37:50 -0000
@@ -155,7 +155,7 @@ SUBST_MESSAGE.mirbsd-paths= Do not use n
 # Remove a spurious workdir reference
 SUBST_CLASSES+=                rm
 SUBST_STAGE.rm=                pre-install
-SUBST_FILES.rm=                lib/Config_heavy.pl
+SUBST_FILES.rm=                config.sh
 SUBST_MESSAGE.rm=      Do not use tools version of rm.
 SUBST_SED.rm=  -e "s!^rm_try='/.*/\\.tools/bin/rm -f!rm_try='/bin/rm -f!"