here-doc in quotes in multiline s//.../e in eval

here-doc in quotes in multiline s//.../e in eval

When <<END occurs on the last line of a quote-like operator inside a
string eval ("${\<<END}"), it peeks into the linestr buffer of the
parent lexing scope (quote-like operators start a new lexing scope
with the linestr buffer containing what is between the quotes) to find
the body of the here-doc.  It modifies that buffer, stealing however
much it needs.

It was not leaving things in the consistent state that s///e checks
for when it finishes parsing the replacement (to make sure s//}+{/
doesn’t ‘work’).  Specifically, it was not shrinking the parent buf-
fer, so when PL_bufend was reset in sublex_done to the end of the par-
ent buffer, it was pointing to the wrong spot.