[perl #19078] wrong match order inside replacement

[perl #19078] wrong match order inside replacement

$ perl -le '$_="CCCGGG"; s!.!@a{print("[$&]"),/./}!g'
[C]
[C]
[C]
[C]
[C]
[C]

What’s happening is that the s/// does not reset PL_curpm for each
iteration, because it doesn’t usually have to.

The RHS’s scoping takes care of it most of the time. This happens with
the /e modifier and with @{...}.

In this example, though, we have a subscript, not a block. This sub-
script is in the same scope as the s/// itself.

The assumption that the substitution operator will never have to reset
PL_curpm itself appears to be incorrect. This fixes it.