That doesn't work because printf requires two arguments, a format string and a list of variables to coerce into the format. If you say printf $newarray (a rather odd choice of variable name, BTW) then you're only sending one argument to printf. You can do what you want by simply doing:

my $format = '%11s %3d %5.1f\n';
printf $format, 'Hello there', 123, $pi;
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