Perl REPLs

[davies]

Whenever I've wanted a Perl REPL, I've used the debugger, at which my expertise is limited. I know there are several others out there, such as Devel::REPL, perlconsole and Carp::REPL. I can't find anything like the one BrowserUK refers to in Re^3: Pick a single item from a sub's return list, but I didn't think the list above was exhaustive anyway. What REPLs does the Monasteriat like & dislike and why?

Regards,

John Davies

[BrowserUk]

My repl is basically the same 15 line perl script I wrote nearly 15 years ago. 3 years ago it looked like this.

Today, it looks like this:

<Reveal this spoiler or all in this thread>

It has at various times had more preloaded stuff, and less; and more and less logic in the loop, but the core 10 or so lines have barely changed at all.

It has never, and will never be published because then someone would want it to "work properly with lexical variables"; "automatically print the results of every evaluation"; and "support strict"; etc. All Of which I have no need for, nor the desire to complicate my single most used perl script ever, by adding.

[Discipulus]

thanks!

L*

[BrowserUk]

Sorry, but my repl still isn't available anywhere. If you download a copy, it becomes your repl; not mine. I hope you understand the difference.

[RonW]

Very useful. Thanks.

[LanX]

> Whenever I've wanted a Perl REPL, I've used the debugger,

let's first name some problems with that statement ^*

• the debugger doesn't print automatically (The P in REPL)
• the debugger is cumbersome with multi-line statements (you need to end every line with \\ )
• it fails to handle lexical variables across lines
• history and navigation isn't available out of the box
• documentation and code are arcane

I'm personally using a patched version, because I really like the

• extensibility with aliases
• it's already integrated in many IDEs.
• the possibility to run bash commands directly
• When "debugging" (i.e. analysing foreign code), I want to have the same tools at hand

The point that stopped me from publishing a forked version was that POD and code is so deeply interwoven, that I couldn't easily fix the command loop.²

So I delayed the project till I have a POD parser ready that creates a separate perl5db.pod.

Even scarier is that perl5db is using code in the main:: namespace which is not really obvious for me. I think it even dates back to the Perl4 era.

Saying this I really advocate fixing it, extending the debugger to a real REPL which comes out-of-the-box would be a great plus for the Perl universe and could even lead to a Shell replacement.

For those interested IPL: PDF and code

PS: you failed to mention other projects

• Kommodo has an integrated REPL
• Sepia is an emacs package
• see also older threads Re: Perl REPLs (older threads)

footnotes

*) to have some criteria for "good" REPLs

2) The command loop, that's several hundred lines of code with regexes "parsing" commands ... but each block included the POD for that command.

How do you refactor linear code where the documentation depends on the order of the code?

I'm a fan of literate programming, but that's a good example of how not to do it. If you keep documentation close to a subroutine, you can still move that sub, not so when interspersed linear code.

[LanX]

Here some older discussions I had in my bookmarks
• I like Python's interactive shell a lot better than Perl's debugger. What are my alternatives?
• RFC: IPerl - Interactive Perl ( read-eval-print loop )
• Using Devel::REPL
•  Interactive Perl Interpreter
• using perldebugger as REPL?
• Interactive post-coloring of readline input?
to be extended. ..

[VinsWorldcom]

I've used Devel::REPL but found too many dependencies. I tried PerlConsole and Perl::Shell but found them lacking all the features I wanted. I rolled my own "borrowing" code from the above. It's not on CPAN since it's not that good, but you can find here if you're interested:

https://github.com/vinsworldcom/PPC/tree/master/lib/PerlApp

It's included as part of a larger Perl project which has the .pl that provides the shell for that specific project. You could of course use that as an example to write your own.

[titivillus]

I'm on to reply these days https://metacpan.org/pod/Reply