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

&pairwise(
  sub { $a => $b },
  \@a,
  ['a'..'d'],
);
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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'];
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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;
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(It would be more sugary if that return could be a last, but ho hum.)