Fix the following build error:
make top_distdir="bxrrdtool-1.6.1" distdir="bxrrdtool-1.6.1" dist-hook
make[2]: Entering directory '/home/vficet/src/rrdtool-1.x'
cd bxrrdtool-1.6.1 && /usr/bin/perl -i -p -e 's/^\1ERSION.+/\1ERSION='1.6002';/' bindings/perl-*/*.pm
Reference to nonexistent group in regex; marked by <-- HERE in m/^\1 <-- HERE ERSION.+/ at -e line 1.
Makefile:933: recipe for target 'dist-hook' failed
dist-hook: VERSION
- $(AM_V_GEN)cd $(distdir) && $(PERL) -i -p -e 's/^\$VERSION.+/\$VERSION='$(NUM_VERS)';/' bindings/perl-*/*.pm
+ $(AM_V_GEN)cd $(distdir) && $(PERL) -i -p -e 's/^\$$VERSION.+/\$$VERSION='$(NUMVERS)';/' bindings/perl-*/*.pm
$(AM_V_GEN)cd $(distdir) && $(PERL) -i -p -e 's/RRDtool 1.GIT, Copyright by Tobi Oetiker/RRDtool '$(PACKAGE_VERSION)', Copyright 1997-'`date +%Y`' by Tobi Oetiker/' src/*.h src/*.c
$(AM_V_GEN)cd $(distdir) && $(PERL) -i -p -e 's/^Version:.+/Version: '$(PACKAGE_VERSION)'/' rrdtool.spec
$(AM_V_GEN)$(PERL) -i -p -e 's/rrdtool-[\.\d]+\d(-[a-z0-9]+)?/rrdtool-'$(PACKAGE_VERSION)'/g' doc/rrdbuild.pod