@hash{@array_of_keys}=@array_of_values;
Is the Perlish way of assigning an array of values to their equivalent keys. You could, (if you enjoy typing), write

for my $index (0..$#array_of_keys){
   $hash{$array_of_keys[$index]}=$array_of_values[$index];
}
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In the line you cite there isn't an array @returned_values it is a hash slice. take a look at the perldata man page for further, better presented, info