Your "trick" doesn't work. You're just duplicating the work the implicit import in use already does. Like I said in my original post, it's *when* it happens that's important.

You have the right idea, but it needs to be done at compile-time. Fortunately, it's very simple since Perl already provides a means of declaring a function that's to be defined at a later time.

sub gettimeofday();

# Eventually.
eval "use Time::HiRes qw( gettimeofday ); 1"
   or die "Unable to load Time::HiRes: $@\n";

print(gettimeofday);
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The parens in "sub gettimeofday();" are only there because Time::HiRes declares the function using that prototype.