fcntl - file control system all
fcntl FILEHANDLE,FUNCTION,SCALAR
Implements the fcntl(2) function. You’ll probably have to say
use Fcntl;
first to get the correct function definitions. Argument processing and value return works just like ioctl() below. Note that fcntl() will produce a fatal error if used on a machine that doesn’t implement fcntl(2). For example:
use Fcntl;
fcntl($filehandle, F_GETLK, $packed_return_buffer);