[sf-perl] randomize particular lines

[Fred Moyer]

Quinn Weaver wrote:
> On Mon, Mar 06, 2006 at 04:05:47PM -0800, Bart Alberti wrote:
>    $word = $words[rand @words]; ## rand returns fractional numbers.
>                                 ## Unfortunately Perl uses floating-point
>                                 ## numbers by default, so it allows
>                                 ## fractional array subscripts.  However,
>                                 ## you can't reliably take the 1.23'th element
>                                 ## of an array.  This expression will
>                                 ## sometimes get you undef, which is
>                                 ## probably not what you want.

I had to get a random index from a set last week in several places in my 
code.  I was using '$word = $words[int(rand(@words))]' (wrapped in a 
subroutine call), but it's a fairly noisy idiom and I ended up using 
'$word = $words[rand(@words)]' as it's a bit easier on the eyes.

Quinn can you explain a bit more how this expression can return undef? 
I'm using it with a defined @words list and haven't run into any 
problems yet.