[perl #123893] Fix hang with "@{"

Commit v5.21.8-320-ge47d32d stopped code interpolated into quote-like
operators from reading more lines of input, by making lex_next_chunk
ignore the open filehandle and return false.  That causes this block
under case 0 in yylex to loop:

	    if (!lex_next_chunk(fake_eof)) {
		CopLINE_dec(PL_curcop);
		s = PL_bufptr;
		TOKEN(';');	/* not infinite loop because rsfp is NULL now */
	    }

(rsfp is not null there.)  This commit makes it check for quote-like
operators above, in the same place where it checks whether the file is
open, to avoid falling through to this code that can loop.

This changes the syntax errors for a couple of cases recently added
to t/op/lex.t, though I think the error output is now more consis-
tent overall.

1 files changed, 2 insertions, 1 deletions

diff --git a/toke.c b/toke.c
index 9e0575c8bf..4910b6bb97 100644
--- a/toke.c
+++ b/toke.c
@@ -4624,7 +4624,8 @@ Perl_yylex(pTHX)
     case 26:
 	goto fake_eof;			/* emulate EOF on ^D or ^Z */
     case 0:
-	if (!PL_rsfp && (!PL_parser->filtered || s+1 < PL_bufend)) {
+	if ((!PL_rsfp || PL_lex_inwhat)
+	 && (!PL_parser->filtered || s+1 < PL_bufend)) {
 	    PL_last_uni = 0;
 	    PL_last_lop = 0;
 	    if (PL_lex_brackets &&