About this mini-article series. Each day for 24 days, I will be reviewing a module that parses command-line options (such module is usually under the Getopt::* namespace). First article is here.

Getopt::Kingpin is a port of Go's kingpin library, written by Masaaki Takasago (TAKASAGO) in 2016. It offers the usual "nowadays standard" features like: short and long options with short option bundling, automatic help/usage message generation, specifying that an option is required, default value, and subcommands. Two extra features are: specifying that an option can be set via environment variable of a certain name, and built-in completion (which is a feature from the original library but doesn't seem to be implemented yet in the Perl port). The Go library also allows templating of help message, and this is not yet supported by Getopt::Kingpin.

Like Smart::Options (reviewed a couple of days ago), kingpin is using the so-called "fluent style" interface, a.k.a. chained methods, which I find annoying to type in Perl due to the method call operator in Perl being -> instead of a single dot. Although fortunately the chained methods interface is slightly less annoying than in Smart::Options.

After looking at the 3 ports of option parsing libraries (the abovementioned two plus Getopt::ArgParse reviewed yesterday) it indeed seems that subcommand support is becoming a standard thing. Which makes me think about whether Getopt::Long should also add such feature, or whether we should promote some other option parsing library as the "best practice" when one wants to do subcommands. So far, I'm not seeing any single best candidate for "Getopt::Long + subcommand support".