$string = "a:b:c";

($line) = split /:/, $string, 0;
print "Split zero times - $line\n";

($line) = split /:/, $string, 1;
print "Split one time   - $line\n";

($line) = split /:/, $string, 2;
print "Split two times  - $line\n";


 outputs:

Split zero times - a
Split one time   - a:b:c
Split two times  - a