Don't Use Local

The short version is you almost never, ever need to use local. Once upon a time, all variables were global. (Bad Perl, bad!) "Okay," they said, "we'll hack in a way to do local variables using the keyword local in Perl 4." That sort of worked, but not very well. So in Perl 5 they came out with my instead. That worked much better. Now they've added our to handle global variables.

Now, the language gurus (you know who you are) will tell you that what I said isn't really true, but it's close enough to true for most cases. (If you don't understand Einstein, Newton was close enough to get by.)

Summarizing, use my for the locals, our for the globals, and pretend that local doesn't exist.

Wally Hartshorn

Comment on Don't Use Local Select or Download Code

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•Re: Don't Use Local by merlyn (Sage) on Sep 27, 2002 at 19:28 UTC
I'm pretty sure `local` existed in Perl 3 as well, and maybe even Perl 2. And you still need `local` to give a temporary value to a package variable, especially a special variable. For example, this is perfectly sane code: `my $slurp_file = do { local $/; # slurp mode... <SOME_HANDLE>; };` [download] This works because the setting for `$/` (a global variable) will be affected for only the duration of the block in which the `local` appears: just long enough to get the value. So, it's not never use `local`, but rather, be sure you know when to use it (rarely) and when not to use it (mostly). -- Randal L. Schwartz, Perl hacker	[reply] [d/l]

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•Re: Don't Use Local
by merlyn (Sage) on Sep 27, 2002 at 19:28 UTC

local

And you still need local to give a temporary value to a package variable, especially a special variable. For example, this is perfectly sane code:

my $slurp_file = do {
  local $/; # slurp mode...
  <SOME_HANDLE>;
};
[download]

$/

local

So, it's not never use local, but rather, be sure you know when to use it (rarely) and when not to use it (mostly).

-- Randal L. Schwartz, Perl hacker

[reply]
[d/l]