java - Anagram code meaning -

in below code, meaning of following line?

m.put(alpha, l=new arraylist<string>()); 

code (for finding anagrams):

try {     scanner s = new scanner(new file(args[0]));     while (s.hasnext()) {         string word = s.next();         string alpha = alphabetize(word);         list<string> l = m.get(alpha);         if (l == null)             m.put(alpha, l=new arraylist<string>());         l.add(word);     } } catch (ioexception e) {     system.err.println(e);     system.exit(1); } 

the part

m.put(alpha, l=new arraylist<string>()); 

could written as

l=new arraylist<string>(); m.put(alpha, l); 

an assignment returns assigned value, why code working.