Hello keepers of knowledge, I have humble request, to shed some light and guide fellow monk apprentice. I stumble across some piece of Perl code, which I cannot really wrap my head around. It suppose to create an intersection of two arrays (with lower casing all characters). 
my @intersection =
    grep { defined }
        @{ { map { lc ,=> $_ } @a } }
           { map { lc } @b };

[download]
I've run it through deparse to see what's not seen by naked eye. 
$ perl -MO=Deparse -e 'my @intersection =
    grep { defined }
        @{ { map { lc ,=> $_ } @a } }
           { map { lc } @b };
'
my(@intersection) = grep({defined $_;} @{+{map({lc $_, $_;} @a)};}{map
+ {lc $_;} @b});
-e syntax OK

[download]

So this explained me that ',=> $_' is actually just ', $_' but is there a reason for using a fat comma, or is it "Winking fat comma" (still dunno why it's used)?
Why 1st map is enclosed by @{} is it dereferencing output of map?

Probably it's something easy. I just want to understand the mechanics and maybe learn something new.


thanks
m.

In reply to Strange grep construct by mzvk

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