[Omaha.pm] print "%hash";

[Travis McArthur]

Jay Hannah wrote:
> I hit this code today
>
>   $body .= "Email Address: ".$$results{email}."%0D%0A" if ($$results{email});
>
> and thought "What? Isn't Perl going to try to interpret "%0D" as a hash?
>
> Nope.
>
> "%hash" is not interpreted at all. It's just a string.
>
> Fun with hashes below...
>
> j
>
>
> $ cat j.pl
> my %j = ( a => 1, b => 2 );
> print %j, "\n";
> print %j . "\n";
> print "%j\n";
>
> $ perl j.pl
> a1b2
> 2/8
> %j
>
>
> perldoc perldata
>    If you evaluate a hash in scalar context, it returns false
>    if the hash is empty.  If there are any key/value pairs,
>    it returns true; more precisely, the value returned is a
>    string consisting of the number of used buckets and the
>    number of allocated buckets, separated by a slash.  This
>    is pretty much useful only to find out whether Perl's
>    internal hashing algorithm is performing poorly on your
>    data set.  For example, you stick 10,000 things in a hash,
>    but evaluating %HASH in scalar context reveals "1/16",
>    which means only one out of sixteen buckets has been
>    touched, and presumably contains all 10,000 of your items.
>    This isn't supposed to happen.
>
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>
>   
That's rather unusual but very useful, I don't know any other language 
that has built in hashing functionality to have that sort of 
instrumentation (regarding allocated buckets versus full buckets).  I 
never knew that!  Awesome stuff, I like how Perl pretty intelligently 
guesses what you want to know, which is nice.  Thanks for bringing this 
up Jay.

Best Regards,
Travis