It looks like it's taking the first element of the array called 'nodes' and converting it into a hash called attrs. Is that correct? my %attrs = %{ $nodes[0] };

Almost right, it's not exactly converting, it's doing a hash dereference, see perlreftut and perlref. Basically:

my %hash = ( foo => "bar" );
my $hashref = \%hash;        # take a reference to the hash
print $hashref->{foo},"\n";  # acccess a value via the ref
my %attrs = %{ $hashref };   # makes a shallow copy
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(In this case, there's a slightly more complicated thing going on in the background, that you don't necessarily need to care about. $nodes[0] is an object, which provides a special behavior when you use it like a hash reference: it returns the attributes of the element as a hash. That's why I can use this object as if it were a hash reference and dereference it, even though it's a much more complex object than just the attributes in a hash - I can call methods on it, etc. It's documented in XML::LibXML::Element under "Overloading".)