my $w= 2;
my $i= int( rand @list );
my $offset= 0+@list - log( rand( exp( (@list-1)*$w ) ) ) / $w;
$offset= int( $offset * (-1,1)[rand 2] );
my $j= abs( $i + $offset );
$j= @list - $j
    if  @list <= $j;