I know many people will disagree with rule 25. But they are my guidelines, and that's the way I code. Not just in Perl, but any language that I can remember programming in allows whitespace between an indentifier and its indexing operation. Including Python. (Unfortunally, Perl 6 will break decades of tradition).

The reason is that the eye needs resting points. Whitespace makes it easier to divide a line of text into chunks and read it. As well as in natural languages as in code. $foo{bar}[17]{baz} is one big blob, and it's hard to divide it into its 4 chunks, specially when the subscripts are a bit more complex. We don't have the tendency to chain words together in English (unlike in for instance German). Why should we with code?

Abigail