/usr/bin/perl5 -p -e 'BEGIN { print qq|$(HASH_LINE) 1 "<Berkeley UPC 2.2.2>"\n|; } \
          if (/^#(?:line)?\s*[0-9]+/) \
            { s)\Q"$(PREPROCNAME)")"$(ORIGNAME)"); s@//@/@g; }' \
            '$<'  > '$@'

It's that ugly.