The South Korean international was named captain for the night as Wolves made eight changes from the side that lost 1-0 at Bournemouth on Saturday.
Wolves were awarded a penalty at the end of the first half after Jean Ricner Bellegarde was felled.
Hwang stepped up to take the spot kick, but his shot cannoned off the post with Rodrigo Gomes scoring from the rebound.
The 29-year-old was replaced in the 80th minutes to cheers from certain sections of the crowd.
"Do you know what happened with Hee Chan this week? His grandfather passed away," said Pereira.
"When I ask him, I said you decide if you want to go to Korea, his grandfather was very close to him.
"And he showed me he wants to help the team, he wants to stay here, he wants to try, he gave everything to help us.
"We need to respect his character a lot and I respect him.
"He is a player I want to keep here."
Hwang will be looking to open his account for the season as Wolves host Everton at Molineux on Sunday.