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

Chas. Owens wrote:
>> w? 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.
>
>
>
>   
thanks Chas, I have cheat sheet on my monitor and I only had qr as 
regex, I am making a note on the fact that it actually compile only once 
regex and
should not be used at all time to do regex build.