sub permute{
@r=[];$e=$_,@r=map{@a=@$_;map{@b=@a;splice(@b,$_,0,$e);[@b]}0..@a}@r for@_;@r
}

##</code><code>##

sub permute{
@r=[];$e=$_,@r=map{@a=@$_;map[@a[0..$_-1],$e,@a[$_..$#a]],0..@a}@r for@_;@r
}