Taking ideas from both my previous post and abstracts post ... we can get down to 105 quite nicely.

@b{@b{0..27}=(_,a..z,'.')}=0..27;@s=pop=~/./g;$p[$_[0]*$_%+@s]=$b{($b{
+$s[$_]}+$_)%28}for 0..$#s;join'',@p
[download]

I especially like the way he does the split I was doing. The comparison is quite stunning.

@e=split//,pop;
@e=pop=~/./g;
[download]

It's only two characters, but it takes advantage of a feature I didn't know about.

The double hash-slice assignment is also quite neat. It saves more characters over what I was doing, but it's not as stunning, in my eyes. *shrugs*

++abstracts!!

Update: Ok, abstracts! *laughs* Let's get below 100. (I'm still trying to figure out why you want to be strict- and warnings-compliant in a golf. To me, it's enough that it runs more than once, if that's what the golf calls for.)

@;{@;{0..27}=(_,a..z,'.')}=0..27;$,=0;$;[$_[0]*$,++%@s]=$;{($;{$_}+$,)
+%28}for@s=pop=~/./g;join'',@;
[download]

99 characters! :)

I'd like to congratulate abstracts on finding some very neat golfing techniques. :)

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/me wants to be the brightest bulb in the chandelier!

Vote paco for President!