And the same with error handling:

use List::Util 'sum';
my $avg = @times ? sum(@times)/@times : "NaN";
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As I just discovered w/ some help on CB, don't expect the above "NaN" to be NaN on MS. s/"NaN"/1e9999\/1e9999/ for portable (and less readable) support there.

Update: ikegami is of course right that it's a C lib problem, not OS dependent, but that does not change that there are potential NaN portability issues.