くいらっしゃいましっちゃう
yokuirasshai mashi' chau

Godan Verb (u)
Interjection

The completive aspect (contracted form) - indicates completion or regret of 良くいらっしゃいました

1. Welcome (past, emphatic, slightly regretful); Welcome (past, overly polite/humble)

Completed Action
Colloquial