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[perl #123712] Fix /$a[/ parsing
The parser used to read more lines of input when parsing code interpo-
lated into quote-like operators, under some circumstance. This would
result in code like this working, even though it should be a syn-
tax error:
s||${s/.*/|;
/s}Just another Perl hacker,
print
"${;s/.*/Just an";
other Perl hacker,
/s} die or return;
print
While this was harmless, other cases, like /$a[/<<a with no trailing
newline, would cause unexpected internal state that did not meet the
reasonable assumptions made by S_scan_heredoc, resulting in a crash.
The simplest fix is to modify the function that reads more input,
namely, lex_next_chunk, and prevent it from reading more lines of
input from inside a quote-like operator. (The alternative would be to
modify all the calls to lex_next_chunk, and make them conditional.)
That breaks here-doc parsing for things like s//<<EOF/, but the
LEX_NO_TERM flag to lex_next_chunk is used only by the here-doc
parser, so lex_next_chunk can make an exception if it is set.