reviewed by brad@
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The File::Tail module is designed for reading files which are
continously appended to (the name comes from the tail -f directive).
Usually such files are logfiles of some description.
The module tries hard not to busy wait on the file, dynamically
calcultaing how long it should wait before it pays to try reading
the file again.
The module should handle normal log truncations ("close; move; open"
or "cat /dev/null >file") transparently, without losing any input.
