Additionally, to make room for Perdomo on the 40-man roster, the Twins transferred right-hander Carl Pavano to the 60-day disabled list. He was originally placed on the 15-day disabled list with a strained right shoulder on June 4.
Swarzak last pitched on Tuesday against the White Sox, when he allowed two runs on two hits in one inning in relief. He has a 4.43 ERA in 69 innings this year, including a 3.02 ERA in 27 relief appearances.
Perdomo, meanwhile, will be making his Twins debut, as he was signed by the club as a Minor League free agent before the season.
The hard-throwing right-hander posted a 0.92 ERA with 18 strikeouts and two walks in 19 2/3 innings at Rochester. He started the year at Double-A New Britain, where he had a 2.75 ERA and 43 strikeouts in 39 1/3 innings.
Perdomo, 28, most recenetly pitched in the Majors in 2010 with the Padres, making just one appearance. It was a year after he made 35 appearances out of the bullpen for the Padres, posting a 4.80 ERA with 55 strikeouts in 60 innings.