If you want to add an element to the middle of an existing array you can use the
splice() function. Splice modifies arrays in place. Splice takes four arguments for this: the array to modify, the index of where you want to modify, the number of items you want to remove, and an array of the elements to add.
my @x = qw(one three); # At the 2nd index, add (replace zero elements) a one element array splice(@x, 1, 0, ('two')); print join(" ", @x); # "one two three"