$ #trace +step +search
$ const systems {{ agaton 'debian' sherlock 'debian' hatebox 'rhel' }}
$ ?
? member_at systems ?Name ?OS
SetValue 0.Name 'agaton'
BindValue 0.OS systems.agaton
? eq OS 'debian'
? ...
{{ Name 'agaton' OS 'debian' }}
{{ Name 'sherlock' OS 'debian' }}
No next solution