# Remove the 4th column.
splice(@$_, 3, 1)
   foreach @$rows;

##</code><code>##

# Swap the 3rd and 4th columns.
splice(@$_, 2, 0, splice(@$_, 3, 1))
   foreach @$rows;

##</code><code>##

# Swap the 3rd and 4th columns.
my @map = (0, 1, 3, 2, 4, 5);
@$_ = @$_[@map]
   foreach @$rows;