To allow for labels you need to block off the code(because I assume you don't wish it for the entire script; but if you did, you still need brackets). This would work for our example:

LINE: { flock(FILE,2) or goto LINE; } #p.s., you should probably
                                      #use the constants provided
                                      #and not numbers like 2
[download]

Update: Yes, labels on single lines can be used. However, in practise, a looping construct(for,while,etc.) is usually better for only a single line. Even then, though, having brackets is best to solve any abiguity that may arise. But yes, a single line label is possible(and useful on some occasions).