A coworker of mine was going over some sort of Perl quiz questions, and I was stumped by this one. The question wants you to remove duplicate values from an array without using a looping construct. This is the answer: 
my @arr = (4, 1, 6, 4, 3, 7);
my %saw;
@saw{ @arr } = ();  # The line I'm not understanding
my @new_arr = keys %saw;
print sort @new_arr;

[download]
Normally I would do this with map(), thusly: 
my @arr = (4, 1, 6, 4, 3, 7);
my %saw = map{ $_ => undef } @arr;
my @new_arr = keys %saw;
print sort @new_arr;

[download]

Which I think is much more clear, but I woud like to understand what the first version is doing. Can someone shed some light on this for me?

I'd do a search, but I'm not sure what to search for.

In reply to De-Duping An Array by SheridanCat

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