Change your "print" statement to :

print "@array\nExtra params: @ARGV";
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and you will see the problem.

The correct way to pass in multiple values is:

  perl  <program>  --prueba2 1  -prueba2  2 --prueba2 3
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You could get the results you are trying without repeating the parameter name, if you use the "experimental" "repeat specifier" getopt feature:

GetOptions ( 
            "prueba2=i{3}" => \@array,
           ) or die "not working: $!\n";
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