I believe that

@all = (\@foo, \@bar);
return @all;
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and

return \@foo, \@bar;
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are identical so far as perl is concerned. Kind of like

print (1, 2, 3, 4);
    # and
print 1, 2, 3, 4;
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Anyway my suggestion is that if you're expecting a set number of elements from a subroutine then you can do something like this:

my ($aryref1, $aryref2) = subroutine();
    # or if you want the longer way.
my $aryref1;
my $aryref2;
($aryref1, $aryref2) = subroutine();
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Note that if a subroutine returns a list and you do something like:

my $ret = subroutine();
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Then $ret will be the number of elements in the list that subroutine returned, not the first.

Jacinta