Re: in the elemetns of programming perl , I need help with 2 lines that I don't understand

On Sun, Jun 1, 2008 at 3:39 PM, Rob Dixon <[email protected]> wrote:
> Dr.Ruud wrote:
>> Richard Lee schreef:
>>
>>> $pattern = '.*(?:' . join('|', @ARGV) . ')';
>>
>> Safer:
>>
>>   $pattern = '.*(?:' . join('|', map quotemeta, @ARGV) . ')';
>>
>> And I would do a qr() on top of that.
>
> How? And why?
snip

how:

my $pattern = '.*(?:' . join('|', map quotemeta, @ARGV) . ')';
$pattern = qr/$pattern/;

why:

To compile the regex.  In the original program, the regexes use the o
modifier to promise that $pattern won't change so the optimizer can
compile the regexes once, but if you use qr// then you don't have to
make that promise and you still only compile the regex once.



-- 
Chas. Owens
wonkden.net
The most important skill a programmer can have is the ability to read.