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Comment by cogman10 | Hacker News Reader

I mean, the combinations of $%@ are really astoundingly bad. $ alone has so many different meanings and operations depending on context. You won't find that sort of thing in any other language. Not even PHP which for some bizarre reason brought $ along for the ride.

Here's a fun exercise, write a dictionary of arrays. Now write a dictionary of 2d arrays.

In any other language, that's hardly a challenge to both read and write such a structure. Not so with perl.

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> Here's a fun exercise, write a dictionary of arrays.

Umm … ok:

my %dict = ( foo => [ 1, 2, 3 ], bar => [ 4, 5, 6 ], );

> Now write a dictionary of 2d arrays.

my %dict2d = ( foo => [ [1, 2, 3], [4, 5, 6] ], bar => [], );

It’s pretty much identical to JS. Not sure how that’s supposed to exemplify how hard it is to write Perl.

I'm not the original comment author, neither am I fluent in Perl. But I suspect they meant nested hashes and not a hash whose values are arrays of arrays. As you point out, the latter is trivial.

To be clear, even a nested hash is all well as long as the depth and the keys are literals (as in your example). It is when keys are dynamic that things get unruly. And god forbid if the _depth_ of nesting is dynamic. All of these are trivial to implement in Python, Ruby, JS, PHP, ...

    %nested = (foo => { bar => { baz => "quux" } });

Access the leaf with

    $nested->{foo}{bar}{baz}

If the keys are in variables, it becomes

    $nested->{$x}{$y}{$z}

For dynamic depth, do you have a specific use case in mind? If I have a tree, I’m probably going to search it rather than using a hardcoded path.

This is why we use strict! The extra arrow is unneeded, as you're working on the actual hash, not a reference to the hash. This is a compiler error with use strict though, so it's not something you would generally be bitten with when writing real code, just internet comments. :)

Whoops, good catch! I had references on the brain. For completeness, that makes it either

    $nested{$x}{$y}{$z}

or after initializing with curly brackets rather than parentheses to construct a new reference to an anonymous hash

    $nested = { … };

and then use the arrow to dereference as in the grandparent.

I think the point is not that Perl's rules don't make sense -- it's that they're much less obvious than those in many competing languages. In Python, lists are `l = [1, 2, 3]` and dicts are `d = {"key": val}`. Both structures can be nested without any change to the semantics.

> $ alone has so many different meanings and operations depending on context.

Used as a sigil, $ always tags a scalar, a single value.

    $foo = 3;

A reference to something else is a single value.

    $bar = [qw/ apple orange banana /];

The special variable $$ is the pid of the current process, borrowed from the shell. Special variables with punctuation names have length at most one. The leading $ is the scalar sigil, and the latter is its name.

Dereferencing a reference to scalar is rarely used and looks like either

    $$baz = $quux;

    ${$baz} = $quux;

In a regex, $ broadly means end of line, but the exact meaning is context sensitive: possibly end of buffer, just before a newline at the end of a buffer, or end of logical line within a buffer. Where it matters, the anchors \z and \Z have less flexible meanings.

Of those, the kinda fuzzy one is $ inside a regex. The rest follow consistent, simple rules. I’m not sure what you mean by different operations on $. Am I skipping a difficult case you have in mind?

I think shells did $ for vars first, then Perl added @ and % for arrays and hashes (and then $ was refs)

$string was in BASIC. I'm sure it's even older, though (the oldest BASIC I've used is GWBASIC).

I thought BASIC had $ at the end, not at the start? It has been a long time since those days, though.

> I mean, the combinations of $%@ are really astoundingly bad. $ alone has so many different meanings and operations depending on context. You won't find that sort of thing in any other language.

I kind of felt lost first getting started with Scala where I felt like there was symbol overload.

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