RE: multiple keys - one value

[merlyn]

my %hash = map { my $item = pop @$_; map { $_, $item } @$_ }
  [qw(HELP ?) => sub { ... }],
  [qw(QUIT EXIT LEAVE) => sub { ... }],
  ...;

-- Randal L. Schwartz, Perl hacker

[japhy]

Thank you, Randal. That looks about right, and perfectly Perlish.

$_="goto+F.print+chop;\n=yhpaj";F1:eval

[bradcathey]

I know I'm only 3 years late, but could someone explain/dissect in teaching terms, just what merlyn did. /msg me if you wouldn't mind so I know it's up. Thanks.

[merlyn]

It'd help if you explained what parts you already do understand, so we don't have to repeat that. Do you know what qw() does? How about map? References? sub{}?

[bradcathey]

Okay, now I'm nervous ;-) My reason for asking is purely academic--I'm trying to REALLY learn Perl (yes I have read the Llama book and am plowing through the Camel tome). However, instead of starting with what I don't understand, let me start with what I do (I do understand your first reply to this post and even much of the Linux article referenced).

It appears that in the first line:

my %hash = map { my $item = pop @$_; map { $_, $item } @$_ }

you are mapping a key and value to %hash from an array. Next, it looks like a string of "HELP" redirects flow to a sub (as does the last line "QUIT"...).

Now, what I don't understand, specifically, how are the keys and values being mapped into the hash (where are they coming from)? What does pop @$_ do (couldn't find @$_ explained anywhere)? How does the last bit on that first line work? map { $_, $item } @$_

Lastly, why are there square brackets bookending lines 2 and 3?

I may not be ready for this heady stuff, but I'm willing to try. Thanks merlyn.

Update:
Thanks to runrig and his reply. I get it in theory, but not in practice. Though it has encouraged a more thorough understanding of map. I'll look at this in a couple of months and probably get it fine. Thanks.