Sucking the hash into a ref would be smarter if it were passed as a ref:

# Call as $obj->foo( { keys => values } )
sub foo {
  my( $obj, $params ) = @_;
  # ..
}
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but here it is not called like that. Indeed, davidrw's code $params = { @_ } copies the hash, as it must, since it is passed that way.

Your other idea is good.