What kind of code that you have written today breaks tomorrow?

• I use hashes, and I index in them.
• I use subroutine/method calls on the LHS of binary operators.

Perhaps I'm mistaken, but looking at your examples, aren't they both aspects of the whitespace-between-tokens issue that was discussed here recently?

Furthermore, I have been under the impression that old code was going to be parsed under a Perl-5-compatibility mode that presumably would use the old whitespace rules... Am I mistaken, or will this allow your old code to still work without change?