use Data::Dumper; print Dumper(+{ unsorted => \@array });
@array = sort {
   $$a[0] <=> $$b[0] or 
   $$a[1] <=> $$b[1] or 
   $$a[2] <=> $$b[2]
} @array;
use Data::Dumper; print Dumper(+{ 
    sorted_on_first_three_elements => \@array });