unfortunately not a perfect solution :(

using literal list is cumbersome

  DB<260> pairwise { $a => $b } @a, @{[a..d]}  
 => (1, "a", 2, "b", 3, "c", 4, "d")
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no warning if $a or $b is lexical

  DB<261> my $a;pairwise { $a => $b } @a, @{[a..d]}      
=> (undef, "a", undef, "b", undef, "c", undef, "d")
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sort does it right

  DB<262> my $a; sort {$a <=>$b} reverse 1..10;;       
Can't use "my $a" in sort comparison at (eval 360)[multi_perl5db.pl:64
+4] line 2.
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and there is no easy way to limit size to one of the arrays like with Hyper-Operators in Perl 6

(update)

@a »+« @b;   # @a and @b MUST be the same size
@a «+« @b;   # @a can be smaller, will upgrade
@a »+» @b;   # @b can be smaller, will upgrade
@a «+» @b;   # Either can be smaller, Perl will Do What You Mean
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