Perl 5 has $[ which lets you set the base for every array. eg. $[ = 1; would cause all arrays to be 1-based. Thankfully they've now deprecated this misfeature ...
I thought that was deprecated a long time ago. When I learned Perl in 2000 I remember I read not to use that "feature". Apparently it was just not recommended, for a very long time.
Certainly the advice has been don't use it for a very long time. At least since the 90s when I learned Perl. However it wasn't actually deprecated until last year (Perl 5.12). There were a sequence of steps leading up to full deprecation which you can read about in the link I provided above. Maybe some people were actually using it?!?
http://perldoc.perl.org/perlvar.html#Deprecated-and-removed-...