Oh, sure. And I don't give a damn about the difference in compilation speed of trivial small regexes.

But when the regexes get large, and difference of compiling the patterns is a few seconds vs a few minutes, I do care.

But still, even in your simple example, it's three compilations + two stringifications vs a single compile.

Here's a benchmark, 1 compilation vs 12 compilations and 20 stringifications: 

use Benchmark 'cmpthese';

cmpthese -1, {
    qq =>  'my $p = qq{a}; $p = qq{$p$p} for 1 .. 10; qr/$p/',        
    qr =>  'my $p = qr{a}; $p = qr{$p$p} for 1 .. 10; qr/$p/',        
};
__END__
       Rate     qr     qq
qr    914/s     --  -100%
qq 283880/s 30949%     --

[download]
That's with 5.15.9 (on OSX). With 5.12.3 (same box), I get: 
       Rate     qr     qq
qr    857/s     --  -100%
qq 324588/s 37769%     --

[download]
And, for kicks, with 5.8.9 (again, same box): 
       Rate     qr     qq
qr    508/s     --  -100%
qq 301810/s 59290%     --

[download]
The resulting patterns, while identical, also differ significantly in size: the one build with repeated qr constructs is 19 times the size of the one build with qq.

I'm usually not a stickler for speed. But I make an exception when it comes to qr.

In reply to Re^9: Common Perl Pitfalls by JavaFan
in thread Common Perl Pitfalls by Joe_

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