You can use fileno to find out if a filehandle is open, but it's a much better idea to make sure the open() succeeded in the first place, as suggested above.

Note: the 'fileno' documentation referred to on perlmonks.org is incomplete. The documentation included with perl 5.6.1 includes this: Returns the file descriptor for a filehandle, or undefined if the filehandle is not open.

Example:

sub chk_hndl {
  if (fileno $_[0]) {
    print "OPEN\n"
  } else {
    print "NOT OPEN\n"
  }
}
chk_hndl(*FOO);
chk_hndl(*STDOUT);

# prints:
NOT OPEN
OPEN
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