[perl #77762] Constant assignment warning

[perl #77762] Constant assignment warning

With this patch:

$ ./perl -we 'sub A () {1}; if (0) {my $foo = A or die}'
$ ./perl -we 'sub A () {1}; if (0) {my $foo = 1 or die}'
Found = in conditional, should be == at -e line 1.

Since the value of a constant may not be known at the time the program
is written, it should be perfectly acceptable to do a constant assign-
ment in a conditional.