use Fcntl; use Fcntl qw(:DEFAULT :flock);
You can request that the flock() constants (LOCK_SH, LOCK_EX, LOCK_NB and LOCK_UN) be provided by using the tag ":flock". See Exporter.
You can request that the old constants (FAPPEND, FASYNC, FCREAT, FDEFER, FEXCL, FNDELAY, FNONBLOCK, FSYNC, FTRUNC) be provided for compatibility reasons by using the tag ":Fcompat". For new applications the newer versions of these constants are suggested (O_APPEND, O_ASYNC, O_CREAT, O_DEFER, O_EXCL, O_NDELAY, O_NONBLOCK, O_SYNC, O_TRUNC).
For ease of use also the SEEK_* constants (for seek() and sysseek(), e.g. SEEK_END) and the S_I* constants (for chmod() and stat()) are available for import. They can be imported either separately or using the tags ":seek" and ":mode".
Please refer to your native fcntl(2), open(2), fseek(3), lseek(2) (equal to Perl's seek() and sysseek(), respectively), and chmod(2) documentation to see what constants are implemented in your system.
See perlopentut to learn about the uses of the O_* constants with sysopen().
See ``seek'' in perlfunc and ``sysseek'' in perlfunc about the SEEK_* constants.
See ``stat'' in perlfunc about the S_I* constants.