He spent a month on loan with fellow Championship club Charlton Athletic at the start of the year in order to gain match fitness but the South Londoners decided against extending the deal.
In a heartfelt message to Middlesbrough fans on the club’s official website, Williams said, “I’ve known the manager at Perth since I was a kid
“He’s a family friend of my parents and obviously with it being my home town club and the team I’ve supported it’s something I’d looked at.
“If I had everything my way I probably wouldn’t be going home this early because I had dreams of getting Middlesbrough promoted and playing in the Premier League.
“But for me personally I knew that I needed to get home to kick-start my career again. With the manager there, the lifestyle and my family around me that’s going to help me play my best football.
“This is my home, really. I’ve had all of my adult life here. I’ve met some great friends and gone through some great managers.
“Obviously the chairman has been there, too, the lads and the staff and it will be difficult leaving.
“But let’s hope I can leave on a high. I’ll give all of my support to the manager and the boys as much as I can to the end of the season. I’m always here to support everyone.”
The Australian international continued, “I’d just like to thank the fans for all they’ve done for me. At the end of the season I’ll have been here 11-and-a-half years.
“They’ve been great towards me and when I was playing they were great.
“It’s good to see them all coming back now and they need to keep getting behind the team like they have done the last two years, pushing them on to where we all want to be.
“There would be no greater feeling for me than to see Middlesbrough go into the Premier League.
“That’s what we need to do. We’re good enough, we’re the best team in the league. All of the lads are hungry and driven, as is the manager and his staff.
“I’ll always support the team. It’s a great bunch of lads, a great manager and staff and I’m here for them all.
“I’d love to be involved but it’s not going to happen, so the next best thing to jump on the wagon with them and support them all the way.
“It’s a great set up and one that deserves to be in the Premier League. I’ve been saying this since we went down. We’ve never been in this situation of being so close so let’s get there together.”
Middlesbrough came within minutes of opening up a four point lead at the top of the Championship last night but were pegged back by a dramatic injury time Michael Keane header, which rescued a draw for second placed Burnley.
Boro face play-off chasing Ipswich at the Riverside on Saturday.