William R. Perl was born to a textile merchant in Prague on September 21, 1906, in what was then the Austro-Hungarian Empire. He spent much of his youth and early adulthood in Vienna. Perl attended the University of Vienna, where he earned a Ph.D. in law and a master's degree in international business. He joined "Ivria", one of several Jewish fraternities, as a student and soon became deeply immersed in the growing Zionist movement. Perl established a successful law firm in Vienna after graduating and practiced law there until the Nazi take-over in 1938.