well ... it really depends on the definition of "rewrite" and the dictionaries are not helpful. °

When in doubt, explain your point:

I can hardly imagine reinventing Perl5 from scratch and keeping that degree of compatibility with Perl4, so he must have reused the old code base somehow (think of all those complex parsing rules alone)

Perl6 on the other hand was recoded from scratch, AFAIK.

°) the German translations include both "reshaping a text" and "writing it new"