syswrite - fixed-length unbuffered output to a filehandle
Attempts to write LENGTH bytes of data from variable SCALAR to the
specified FILEHANDLE, using the system call write(2). It bypasses
stdio, so mixing this with prints may cause confusion. Returns the
number of bytes actually written, or undef if there was an error. An
OFFSET may be specified to place the read data at some other place than
the beginning of the string.