Perl’s basic data type is the scalar, which takes its name from the mathematical term for “single item”. However, the scalar is really two things. You probably know that a scalar can be either a number or a string, or a number that looks the same as its string, or a string that can be a number. What you probably don’t know is that a scalar can be two separate and unrelated values at the same time, making it a dualvar. Continue reading “Create your own dualvars”
Category: book
Make disposable web servers for testing
If you project depends on a interaction with a web server, especially a remote one, you have some challenges with testing that portion. Even if you can get it working for you, when you distribute your code, someone else might not be able to reach your server for testing. Instead of relying on an external server, you can use a local server that you write especially for your test suite. Continue reading “Make disposable web servers for testing”
Know split’s special cases
Perl’s split has some special cases and some perhaps surprising cases. The empty pattern, zero width match, the special argument ' ', and the /^/ act differently than you might expect from the general rule. Continue reading “Know split’s special cases”
Trace your Perl programs
You can write your own mini (or micro) debuggers to watch your program run. You might want to do this when the other Perl debuggers are too heavyweight (or even too interactive) for your immediate problem. Continue reading “Trace your Perl programs”
Use Data::Printer to debug data structures
You can use several different Perl modules to inspect data structures. Many of these modules, however, are really two tools in one. Besides showing a data structure as a string, they also serialize the data as Perl code so you can reconstruct the data structure. That second job often makes things hard for you. If you don’t need the serialization job, don’t use a module that insists on it. Continue reading “Use Data::Printer to debug data structures”
Make grep-like syntax
To create grep– or map-like syntax, you need to use Perl’s prototypes, despite whatever we told you in Understand why you probably don’t need prototypes. Perl needs the special hints that prototypes to parse a block as an argument to a subroutine. Continue reading “Make grep-like syntax”
Profile with Devel::NYTProf
Profile before you decide where to optimize—you might be surprised where you’re losing all of your performance.
We won’t go into all the details of profiling in this Item, but you can read about those in Mastering Perl. In short, profilers count something then report the results. They can track any of the things that you might care about. The Devel::NYTProf module, like most profilers, tracks time, counting the statements you run and how long they take. Continue reading “Profile with Devel::NYTProf”
Use lookarounds to split to avoid special cases
There are some regular expression tricks that can help you deal with balanced delimiters in a string. The split command takes a pattern, removes the parts of a string that match that pattern, and give you a list of the parts of the string between those separators. Said another way, split works when the parts you don’t need are between the values. Continue reading “Use lookarounds to split to avoid special cases”
Understand why you probably don’t need prototypes
You should understand how Perl’s prototypes work, not so you’ll use them but so you won’t be tempted to use them. Although prototypes can solve some problems, they don’t solve the problems most people want. Continue reading “Understand why you probably don’t need prototypes”
Return error objects instead of throwing exceptions
Programmers generally consider two types of error communication: the “modern” and shiny exception throwing, and the old and decrepit return values. When they consider these, they choose one and forsake the other. One is good, and the other is bad. Programmers won’t agree on which is which though. Continue reading “Return error objects instead of throwing exceptions”