Sorry, I should have broken it down for you.

@Stuff{@{$Types{$_[0]}}} = @_;
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Working from the inside out. $_[0] is the 0^th element of @_. If its value is "addr", then the value of $Types{"addr"} is \@Address (a reference to the global @Address).

@{\@Address} takes the reference and "returns" the array it points to. @Stuff{@Address}, known as a "hash slice", is assigned the values in the @_ array, and is equivalent to this:

@Stuff{@Address} = qw(addr bob smith '1234 main st' anytown 20500);
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A hash slice is just shorthand for this:

$Stuff{type} = 'addr';
$Stuff{firstname} = 'bob';
...
$Stuff{zip} = '20500';
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[I hope that was clear]