in reply to import doesn't work at runtime?

In perldoc perlsub we read:
A subroutine may be called using an explicit & prefix. The & is optional in modern Perl, as are parentheses if the subroutine has been predeclared.

So, unless you have predeclared your subs, you cannot call a sub without the parentheses. A non-predeclared sub without parentheses is just a bareword.

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

In Section Seekers of Perl Wisdom