Yet Another Perl Switch Statement

Matthew O. Persico — Wed, 23 Mar 2022 15:56:58 +0000

I am in the middle of a project at my job where we are converting some Perl to Python :-(. In the conversion I was explaining this invocation of a switch statement:

for (ref($thing)) {
    /ARRAY/ && do {
        some_array_thing($thing);
        last;
    };
    /LIST/ && do {
        some_list_thing($thing);
        last;
    };
    ## default;
    some_scalar_thing($thing);
}

After explaining how the for statement sets $_, I was asked, "Why not just set $_?"

Indeed, why not? You can play with the following code here: http://tpcg.io/KN9H82

use strict;
use warnings;

{
    local $_ = 'foo';
    /bar/ && do { print 'we got bar'; last };
    /foo/ && do { print 'we got foo'; last };
    /eek/ && do { print 'we got eek'; last };
    print 'we dropped through';
}

with output

we got foo

So, my questions are:

Why have I never seen this in any discussion of Perl's switch synonyms?
Is there any inherent problem with this?

Perl Lists - a Partial Taxonomy

Matthew O. Persico — Tue, 25 May 2021 00:58:54 +0000

Mark Garder recently published the article A list of Perl list processing modules, a detailed and factual, unopinionated listing of eight Perl modules that manipulate lists. So, naturally, when his factual, unopinionated listing was cross posted to Redit, the first comment was the emotional, highly opinionated: “So how do we go about fixing this mess? Because it is a mess.”.

Yes, the comment was mine.

My intent was to see if we could create One List:: To Rule Them All. Not only does it confuse people who want to learn Perl to have various list functions in different modules (and to have functions that share a name across modules work differently), but it also confuses Perl veterans.

And yes, once again, that’s me.

After some consideration, some education and a conversation with the current maintainer of List::Util, the module of list functions that come with Perl itself, it seemed to me that the first order of operations was to detail just how much of a “mess” this was. So, on Sunday afternoon, while waiting to go to the airport to pick up my son, and while watching Phil Mickelson winning the PGA championship at a record 50 years old, I put together the following spreadsheet:

https://docs.google.com/spreadsheets/d/11gI89kOJvm5b30jEWrLaL0D77sZnPKMhMeAP5WcFnzs/

I hope that this can serve a as reference for people to see what's available and where it is available. Yes, it may not have a long shelf life, but I learned a bit more about the state of the List:: namespace. Hopefully, you'll learn a bit too.

DEV Community: Matthew O. Persico

Yet Another Perl Switch Statement

Perl Lists - a Partial Taxonomy