What is meant is that use strict; requires that variables be initialized.

To quote from the perldoc:strict where strict vars is implied by not specifying what to be strict about:

     "strict vars"
           This generates a compile-time error if you access a
           variable that wasn't declared via "our" or "use vars",
           localized via "my()", or wasn't fully qualified.
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The use vars qw($OURVAR) = (); pragma actually declares the variable $OURVAR and initializes it to a known null value instead of leaving it uninitialized. Perl cares about the difference.

-Kurt