Set PL_expect only once after curly subscripts

Set PL_expect only once after curly subscripts

When curly subscripts are parsed, the lexer (toke.c:yylex) notes that
the value of PL_expect needs to be set to XSTATE (expecting a state-
ment) after the final brace.  When the final brace is encountered,
PL_expect is set to that recorded value.  But then the parser
(perly.y) sets it to XOPERATOR immediately thereafter.

This approach requires a plethora of identical statements in perly.y.
If we just set PL_expect to the right value to begin with, we can
avoid all those assignments.