When लिङ् is निमित्त and there is violation/barring of the verb in future tense (i.e. the scenario is that the verb action would be cancelled) then we have लृङ्. For example, श्रमश्चेदकरिष्यद् उत्तीर्णोअभविष्यत् (if you don't work hard, you won't pass).