Closes the file or pipe associated with the file handle, returning TRUE only if stdio successfully flushes buffers and closes the system file descriptor. Closes the currently selected filehandle if the argument is omitted.
You don't have to close FILEHANDLE if you are immediately going to do another open() on it, because open() will close it for you. (See open().) However, an explicit close() on an input file resets the line counter ($.), while the implicit close done by open() does not.
If the file handle came from a piped open close() will additionally return FALSE if one of the other system calls involved fails or if the program exits with non-zero status. (If the only problem was that the program exited non-zero $! will be set to 0.) Also, closing a pipe waits for the process executing on the pipe to complete, in case you want to look at the output of the pipe afterwards. Closing a pipe explicitly also puts the exit status value of the command into $?.
Example:
open(OUTPUT, '|sort >foo') # pipe to sort
or die "Can't start sort: $!";
#... # print stuff to output
close OUTPUT # wait for sort to finish
or warn $! ? "Error closing sort pipe: $!"
: "Exit status $? from sort";
open(INPUT, 'foo') # get sort's results
or die "Can't open 'foo' for input: $!";FILEHANDLE may be an expression whose value can be used as an indirect filehandle, usually the real filehandle name.