A 4 space indent is fairly conventional in the Perl world, but really is not critical in any sense. In a C++ context I use a 3 space indent because 2 is too few for me to be able to see correctly a lot of the time and 4 leads to stuff disappearing off the right edge too fast. I use a 4 space indent for Perl because that is most common. Sometimes it is just best to go with the flow!

Personally I really dislike white space on the inside of parenthesis ( like this ), but if you are going to do it at least be consistent (why should the rule be different for while than for for?).

Where there is no other compelling reason to choose one formatting option over another I choose the one that results in code looking the most like conventionally formatted English prose. That is what I parse most and I figure the more my code parser is like my prose parser the fewer parsing errors I'll get.