On Thu, Sep 30, 2010 at 01:43:06PM +0000, Ãvar ArnfjÃrà Bjarmason wrote:
> Change the regex fragment in extract_valid_address to use the qr//
> syntax for compiled regexes, and when they're used add a /o flag so
> they're only compiled once for the lifetime of the program.
> [...]
> sub extract_valid_address {
> my $address = shift;
> - my $local_part_regexp = '[^<>"\s@]+';
> - my $domain_regexp = '[^.<>"\s@]+(?:\.[^.<>"\s@]+)+';
> + my $local_part_regexp = qr/[^<>"\s@]+/;
> + my $domain_regexp = qr/[^.<>"\s@]+(?:\.[^.<>"\s@]+)+/;
>
Hmm. But these are lexical variables, so won't we recompile them each
time we enter the subroutine? I don't think it affects correctness, as
this "/o":
> + return $address if ($address =~ /^($local_part_regexp)$/o);
means that we will compile and use the value from the first time we run
the function.
But we are unnecessarily compiling the sub-regexes each time. Not that
this is probably a performance critical piece of code, but your "/o" is
doing very little, and this is exactly the sort perl wankery that I find
interesting.
Sadly, there is no real perl equivalent of C static local variables,
which is what you really want. Usually I would do:
{
my $local_part_regexp = qr/.../;
sub extract_valid_address {
...
}
}
but beware of the execution order. That works well in a module, where
the module code is executed before anybody calls the function. But it
breaks in something like this:
foo();
{
my $foo_static_local = 5;
sub foo {
print "$foo_static_local\n";
}
}
I think you could get by with:
{
my $local_part_regexp;
sub extract_valid_address {
$local_part_regexp ||= qr/.../;
...
}
}
-Peff
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