You've got several very good responses. Now here's a craptacular bit of code:

#!/usr/bin/perl -w
use strict;
use warnings;

my @arA = ('alpha', 'beta', 'delta', 'omega');
my @arB = ('alpha', 'foo', 'bar', 'omega', 'baz', 'beta');
my @arC = ('delta', 'grond', 'floo', 'delta', 'omega');
my @all = ();

for my $elA (@arA) {
        my $idx=0;
        for my $elTest (@arB, @arC) {
                ++$idx;
                next unless $elA eq $elTest;

                if ($idx <= @arB) {
                        push @all, $elTest . " - from Array B";
                        next;
                }
                $idx -= @arB;

                if ($idx <= @arC) {
                        push @all, $elTest . " - from Array C";
                        next;
                }
                $idx -= @arC;

                # ... etc.
        }
}

print join("\n",@all);
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