Category: book

Use the \N regex character class to get “not a newline”

Perl 5.12 introduced an experimental regex character class to stand in for every character except one, the newline. The \N character class is everything but the newline.

In prior versions of Perl, this is the same thing as the . meta character. That is, it’s the same as long as someone doesn’t add the /s to the match or substitution operator or the regex quoting operator, or doesn’t insert the option inside the pattern: Continue reading “Use the \N regex character class to get “not a newline””

Use a smart match to match several patterns at once

The smart match operator (Item 23. Make work easier with smart matching) reduces many common comparisons to a few keystrokes, keeping with Perl’s goal of making the common things easy. You can use the smart match operator to make even less common tasks, such as matching many regular expressions at the same time, just as easy. This Item shows you how to use the smart match to see if at least one of a series of regexes matches a string. Continue reading “Use a smart match to match several patterns at once”

Perl 5.14 adds non-destructive transliteration

[This is a mid-week bonus item since it’s so short]

In Perl 5.13.2, you got a non-destructive version of the substitution operator (Use the /r substitution flag to work on a copy). Instead of changing it’s target, the non-destructive version returns a new string that has the substitution. Continue reading “Perl 5.14 adds non-destructive transliteration”

Find a module’s release managers

The CPAN ecosystem is more than just a way to share your code with other people. It’s also a way to let other people collaborate on the code and to help you release it. In Item 70. Contribute to CPAN, you saw how to upload your work to the Perl Authors Upload Server (PAUSE). There’s a lot more that you can do through PAUSE, though. Even if you aren’t a CPAN author, you can use PAUSE to find out more about a module’s authors and comaintainers. Continue reading “Find a module’s release managers”

Count the number of times a character occurs in a string

This Item isn’t really about counting characters in a string, but we thought we’d expand on an Item in the original Effective Perl blog that Joseph set up to support the first edition of Effective Perl Programming. He had an Item titled “Counting the Number of Times a Character Occurs in a String”. We won’t reproduce it here, so you should read his version too. Continue reading “Count the number of times a character occurs in a string”

Force install a module to reinstall it

[This is a midweek bonus Item since it is so short]

I recently bought the new MacBook Air, which means my solid state device has over four times the storage as my old MacBook Air. For the first time, I used Apple’s migration tool to transfer everything from the old one to the new one. It even transferred my perl installations, and I thought that would be fine. It mostly is, except for some compiled modules that cause strange, new errors. Programs don’t load correctly, modules don’t compile, and things go horribly wrong when running test suites. Continue reading “Force install a module to reinstall it”

Make exclusive flip-flop operators

In Respect the global state of the flip flop operator, you saw some examples of the .. scalar operator. The flip-flop operator returns false until its lefthand side is true. Once the lefthand side is true, the flip-flop operator returns true until its righthand side is true. Once the righthand side is true, the flip flop operator returns false: Continue reading “Make exclusive flip-flop operators”

Use CORE when you need the real thing

Perl’s a dynamic language, which means you get to change the definition of almost anything while the programming is running. You can even change the defintions of Perl’s built-in subroutine. Once you (or the evil doer who wrote the module you need) change the definition, you might want to get back to the original, and Perl provides a way for you to do that. Continue reading “Use CORE when you need the real thing”