use strict;
use warnings;
use Data::Dumper;


my @array = ( 0 .. 12 );

my @newarray;

@newarray[ 0 .. 2 ] = ( 
                  [ @array[ 0 .. $#array * .333 ]                 ],
                  [ @array[ $#array * .333 + 1 .. $#array * .667] ],
                  [ @array[ $#array * .667 + 1 .. $#array ]       ] 
);

print Dumper @newarray;