Well, you could write a Template::Plugin that makes available a keys/sort/sortedkey function, so you could write sortedkeys(kw) and it'd work

Or you could write a class to call vmethods and use it with Template::Plugin::Class like

[%
USE vm = Class('TemplateX::VMethodCaller');
FOR k IN vm.sort( vm.keys(kw) ); %]
[download]

Look inside Template::VMethods and Template::Stash (esp dotop)

Or you could realize that keys isn't a particularly swell keyname :) and change it -- unless you're programming a piano/keyboard :p