RE: (Aighearach) Re: Efficient Perl Programming

[Fastolfe]

I was a little more interested in finding documentation (perldoc-style if nothing else), or a niche waiting to be filled by some useful documentation, on general optimization tips (e.g. use !/\S/ instead of /^\s*$/ and why). This information might still be useful to others though. Thanks.

[Dominus]

Here's one rule you might like: It is almost always a mistake to use the non-greedy regex quantifiers like *? and +?.

Typical code looks like this:

    $churchill = qq{"If I were your husband," he said, "I should drink
+ it."};

    while ($churchill =~ /"(.*?)"/g) {
      print $1, "\n";
    }

The purpose of the (.*?) is to capture a quoted part of the string in $churchill. Beginners usually try (.*) which doesn't work, because it captures everything from the first quotation mark to the last, including the non-quoted part in between. So then they ask how to fix this and are advised to use (.*?) instead. This does work, but it's much slower than it needs to be. A faster solution is:

    while ($churchill =~ /"([^"]*)"/g) {
      print $1, "\n";
    }

This says that what you're interested in is a quote character, followed by a sequence of characters that are not quotes ([^"]) followed by another quote. The description of what you want is more exact, and it enables Perl to do the matching more efficiently.

So a good rule of thumb is to avoid .*? wherever possible and to use something like [^"]* instead when you can.

[Aighearach]

Oh, sorry. Maybe this will be more to your liking then:

perldoc Devel::OpProf

Paris Sinclair    |    4a75737420416e6f74686572
[e-mail]    |    205065726c204861636b6572
http://sinclairinternetwork.com

[Fastolfe]

I'm going to ignore the attitude for the moment. Perhaps you misunderstand what I was requesting.

How do I work with Perl references? is to perldoc perlref as What are some approaches I can take while writing code to ensure it is efficient? is to _______________

Lots of others have pointed out some very good books and other various online resources, which is basically what I was looking for. Yes, I see that your Devel::OpProf module can be useful in post-development optimization, but I was looking for something more along the lines of education. I apologize if that was unclear, but I don't appreciate the smart-alec attitude.