Spending your birthday in jail ain't so bad. Not when you get to walk out the next day after waiting 12 years.

Joseph Merlino, the revered and reviled former Philadelphia mob boss who turned 49 on Sunday, began a new chapter this week in his oft-chronicled life as he drove from a federal prison in Indiana to a halfway house in Florida.

"He's just happy to be out," his attorney, Edwin Jacobs, said yesterday. "It's over."

Merlino, arrested in 1999 and convicted of racketeering charges in 2001, will do six months in a halfway house in the West Palm Beach area. Then, he plans to live with his wife, Deborah, and daughters, Nicolette, 14, and Sophia, 13, in Florida, Jacobs said.

"Skinny Joey," by the way, isn't so skinny these days, Jacobs said. He's ripped. Apparently, he hit the weights while in prison.

"He's a real specimen," Jacobs said, repeatedly dodging questions about Merlino's future and what type of career he intends to pursue.

"What he does for a living is his business," Jacobs said.

Unless, Philadelphia law-enforcement officials would point out, he gets back into the old "business" of organized crime.

Asked if Merlino plans to steer clear of the South Philly underworld, Jacobs said, "He's 1,500 miles away." He declined to reveal how Merlino would earn a legitimate income in Florida.

With the flashy gangster in prison, the Philadelphia mob has been a relatively subdued group, which is exactly how reputed boss Joseph "Uncle Joe" Ligambi wants it. Even law-enforcement officials admit that Ligambi, 71, has run the organization more "prudently."

"They are considerably quieter, old-school, more low-profile," a law-enforcement source said. "They aren't going around seeking publicity and making a spectacle of themselves in nightclubs and seeking out media attention."

But they haven't been able to avoid the attention of federal investigators. Merlino's release comes as Philly mobsters brace for an indictment that could name Ligambi, who authorities say took over for Merlino when he was arrested in 1999.

Merlino, however, appears to be in the clear for now, according to attorney Christopher Warren, who was his co-counsel in a 2004 murder trial in New Jersey. The jury found Merlino not guilty.

"They are loath to let you go if it is their intention to bring new charges against you," Warren said. "He's going to try to get himself together and hope that the federal government doesn't bother him anymore."