sub postamble
	{

BLIB_BASE=`$(PERL) -MFile::Basename -e 'print dirname $$ARGV[0]' $(INST_BIN)`
HS_BLIB=$(BLIB_BASE)/my_code

MY_CODE_SHARED_BDIR=$(HS_BLIB)/shared
[and several more similar lines using the HS_BLIB constant]
etc...