use strict;
use warnings;

use Data::Dumper;
$Data::Dumper::Sortkeys = 1;
$Data::Dumper::Indent   = 0;

sub array_fold {
    my $a1 = shift; my @a1 = @$a1;
    my $a2 = shift; my @a2 = @$a2;
    my $folder = shift || sub { [ @_ ] };

    die "Arrays are not of the same size"
        unless scalar( @a1 ) == scalar( @a2 );

    my @results;
    while( scalar( @a1 ) && scalar( @a2 ) ) {
        push @results, $folder->( shift( @a1), shift( @a2 ) );
    }
    return @results;
}

my @a = qw( a b c d );
my @b = qw( A B C D );

my @results = array_fold( \@a, \@b );
print Dumper( { results => \@results } ), "\n";

my @results2 = array_fold( \@a, \@b, sub { "@_" } );
print Dumper( { results2 => \@results2 } ), "\n";

__END__
$VAR1 = {'results' => [['a','A'],['b','B'],['c','C'],['d','D']]};
$VAR1 = {'results2' => ['a A','b B','c C','d D']};