Good programming style: High Cohesion, low coupling. That doesn't only apply across modules, but also applies to functions and code within the same module.

I will use a small sub to return the count so that how you actually implement the count is abstracted from the caller's logic:

for $i (0..varcount($some_variable)) {
  ...
}

sub varcount
{
  # you can implement the count any way you like
  # and change the implementation any time you like, 
  # the caller will not get affected, as long as the
  # interface to varcount is unchanged
}
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