% perl -le '$, = ""; print 1..10' 
12345678910

% perl -le 'print 1..10' 
12345678910

% perl -le '$, = " "; print 1..10' 
1 2 3 4 5 6 7 8 9 10

% perl -le '$, = " abc "; print 1..10' 
1 abc 2 abc 3 abc 4 abc 5 abc 6 abc 7 abc 8 abc 9 abc 10