{  
 my $initialized;
 my @array;
 sub example {
     unless ( $initialized) {
         $#array = $size_needed;
         $initialized++;
     }
      # fill the array
 }
}

##</code><code>##

sub example {
    my @array;
    $#array = $size_needed;
    # fill array -- this is where you may save time
}