resolve #1 - fix warnings new since perl 5.21.2

Redundant argument in %s - this is because the various calls to the
sprintf function offset the arrays by 1 (since the first element of
the array is the sprintf string) but use @_ (the number of elements
in the array) in the range: 1 .. @_

since it's offset by 1 we are going beyond the end of the array and
so sprintf consequently warns that we sent more arguments than it
expected. fix this by using @_ -1 in the range (number of elements
in the array minus 1)