Is ghusl required if a fluid is discharged without arousal after waking up and before Fajr prayer?

If a sleeping person wakes up and finds semen on his garment, he must perform ghusl, even if he did not feel a wet dream. If he doubts the type of fluid, whether it is semen or madhiy, he has a choice: if he wishes, he can consider it semen and perform ghusl, or if he wishes, he can consider it madhiy, wash what it stained, perform wudu, and pray.