Just because I find the subject of lists and the comma operator interesting (and I'm trying to avoid real work for a few minutes):

Compare the outputs of the following assignment expressions:

sub context {
    print
        defined wantarray
        ? wantarray ? "list" : "scalar"
        : "void"
        , "\n";
    $_[0];
}

($a, $b) = (context('a'), context('b'));
print "a=[$a],b=[$b]\n\n";

($a, $b) = (context('a'), context('b')) || die "foo";
print "a=[$a],b=[$b]\n";

list
list
a=[a],b=[b]

void
scalar
a=[b],b=[]
[download]

It appears to me that in the second case the comma is acting as a scalar comma expression and not a list. Granted, || is a binary, not a unary operator, but I find the following description of context supplied in comma expressions interesting:

from the perl 5.8 perlfunc scalar() section:

Because "scalar" is unary operator, if you
accidentally use for EXPR a parenthesized
list, this behaves as a scalar comma expression,
evaluating all but the last element in void context
and returning the final element evaluated in scalar
context. This is seldom what you want.
[download]

Example:

$c = scalar(context('a'), context('b'));
print "$c\n";
void
scalar
b
[download]