I'm intrigued by what you expect keyattr => 1 to do.

Setting KeyAttr to a scalar like this ...

my $opt = XMLin($xml, KeyAttr => 'kool', forcearray => [ 'trans' ]);

... probably ought to throw an exception, but in fact it's an undocumented way to do this ...

my $opt = XMLin($xml, KeyAttr => [ 'kool' ], forcearray => [ 'trans' ]);

... but setting it to '1' makes no sense at all since '1' is not a valid name for an XML attribute. Perhaps what you want to do is turn array folding off altogether, in which case you should set KeyAttr to an empty list:

my $opt = XMLin($xml, KeyAttr => [ ], forcearray => [ 'trans' ]);