Current Perl documentation can be found at perldoc.perl.org.
Here is our local, out-dated (pre-5.6) version:
This should rarely be necessary, as the Perl
close() function is to be used for things that Perl opened itself, even if it was a dup of a numeric descriptor, as with
MHCONTEXT above. But if you really have to, you may be able to do this:
require 'sys/syscall.ph'; $rc = syscall(&SYS_close, $fd + 0); # must force numeric die "can't sysclose $fd: $!" unless $rc == -1;