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")
[download]

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")
[download]

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.
[download]

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
[download]

For literal lists, I'd probably bypass the prototype:

&pairwise(
  sub { $a => $b },
  \@a,
  ['a'..'d'],
);
[download]

Or if you need to do it a lot, maybe wrap it with a different prototype:

sub ref_pairwise (&;@) { goto \&List::Util::pairwise }

ref_pairwise { $a + $b } \@a, ['a'..'d'];
[download]

Limiting to the size of the arrays needs to be added explicitly to the block, but isn't especially challenging:

use v5.12;
use List::MoreUtils;

my @arr = qw/a b c d e/; 
my @bar = qw/12 34 56/; 
my $i = 0;

List::MoreUtils::pairwise {
    return if $i > $#arr || $i > $#bar;
    say "\t$i";
    say "\t\t$a, $b";
    $i++;
} @arr, @bar;
[download]

(It would be more sugary if that return could be a last, but ho hum.)

use Moops; class Cow :rw { has name => (default => 'Ermintrude') }; say Cow->new->name

Nice, but...

return if $i > $#arr || $i > $#bar;

...doesn't report "different numbers of elements."

If I've misconstrued your question or the logic needed to answer it, I offer my apologies to all those electrons which were inconvenienced by the creation of this post.