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

my @foo = ([qw(one two)], [qw(three four)], [qw(five six)]);
use List::Util 'reduce';

my $str = reduce {"[$a,$b]"} map { reduce {"[$a,$b]"} @$_ } @foo;
print "--- $str ---\n";

my $seen = 0;
$str = reduce { $seen++ ? $a.",[$$b[0],$$b[1]]"
                        : "[$$a[0],$$a[1]],[$$b[0],$$b[1]]"
              } @foo;

print "--- [$str] ---\n";
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