|Perl: the Markov chain saw|
Re: Detecting scoping/namespace conflictsby stephen (Priest)
|on Apr 03, 2002 at 22:10 UTC||Need Help??|
I'll start with a brief discussion of my and local. However, the best way of dealing with this situation is to pull out the $localdata assignment into a subroutine. See the end of this note for a discussion of that.
Good: use 'my' not 'local'
Use my not local. local is used primarily for making a local-scope copy of a global variable; for example:
my, on the other hand, always creates a new lexically-scoped variable that is only visible in the enclosing block or file. Use my for all of the variables that you yourself create. So, to modify your code:
Note: code untested
Better: Refactor To Subroutine
Problem is, $usefuldata serves no purpose here except as a placeholder. Nobody is incrementing it; nobody is altering it. It's either 1 or 2. (I know this is a simplified case, but the point still holds no matter how complex the logic.) It's far better from your code's standpoint to pull out the code that calculates $usefuldata into its own subroutine.
Note: Code untested
An advantage to this is that you've eliminated $usefuldata entirely, and never need to wonder if somehow some other bit of code might have altered it. Everything having to do with $usefuldata is in one place.
Gets off soapbox
Update: Looking back, I'm not quite sure if you intended '1' to be the default case, or if the other $usefuldata was completely unrelated. This note assumes that you intended '1' to be inserted if your 'if' statement was false. In any case, replacing the variable assignment with a subroutine will solve the problem, because redefining a subroutine will cause a warning under '-w' anyway.