True and good advise.

The programmer can also use time outs and alarms to walk out of a blocked IO call. Examples of this exist in the perlipc documentation (man perlipc ; perldoc perlipc). (might only work safely on UNIX though).

This will solve your retry problem too. On failing a blocking IO operation, the cautious always pause before trying again. Also be careful of the advisory nature of the flock. A program is not forced to wait unless they lock and unlock voluntarily at the correct place in their operations.
-- termix