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Re: Common Perl Pitfalls

by JavaFan (Canon)
on Apr 10, 2012 at 06:49 UTC ( #964264=note: print w/replies, xml ) Need Help??

in reply to Common Perl Pitfalls

Of course if you had meant the string $to_replace is an actual regex to match against, you're better off using the qr operator:
I don't get this point. You started off that section with:
$to_replace='some_string'; $my_string=~ s/$to_replace/$better_data/;
and doomed this catastrophically unsafe, because $to_replace may actually contain characters that have a special meaning.

But if $to_replace is actually a regexp, the premises is gone -- any special characters are intentional. In fact, it's quite fine in that case to use the above.

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Re^2: Common Perl Pitfalls
by Joe_ (Beadle) on Apr 10, 2012 at 18:21 UTC

    I actually meant to say that one shouldn't use a scalar as a regex anyway. I meant to say that, even if your correct semantics didn't require the use of \Q and \E (i.e. you actually needed the metacharacters) then you're better off using the qr// operator instead of building your regex as a literal string.

      Well, that's nice you want to say that, but can you back up your statement with an argument?

        Several, actually.
        For starters, I happen to believe it's better for readability. Another thing is, the regex modifiers "come with it". So you can include things like the 'x' modifier right along with the regex; if you're using a string as a regex, on the other hand, you have to remember which modifiers you need when you finally decide to use it in a match.
        Also, even though it doesn't show in this example, qr// is more efficient as (IIRC) it pre-compiles its regex before matching: i.e. you can build the regex once and use it several times. I use the qr// operator this way to make my regexes "modular".
        Anyway, you already know that I've been wrong about efficiency before :), so please correct me if you have a different say on the matter. I'm here to learn...

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