It got something to print out at all. Positive step. A vector, according to the module, is similar to a blessed array reference. The exact output is

  The vector of Atom (0, 5, 5)is : %f
{0, 5, 5} The vector of Atom (1, 2, 3)is : %f
{1, 2, 3} The vector of Atom (3, 5, 6)is : %f
{3, 5, 6} The vector of Atom (2, 5, 2)is : %f
{2, 5, 2} The vector of Atom (5, 5, 5)is : %f
{5, 5, 5} The vector of Atom (5, 5, 6)is : %f
{5, 5, 6}
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Which is progress.