use Fcntl qw(F_GETFL O_APPEND);
sub is_append {
  my $fh = shift;
  my $status = fcntl($fh, F_GETFL, 0);
  return $status & O_APPEND;
}
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use FileHandle::Fmode qw(:all);
#$fh and FH are open filehandles
print is_R($fh), "\n"; #it return true if file open in read mode
print is_W(\*FH), "\n";#it return true if file open in write mode
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use warnings;
use Inline C => Config =>
    BUILD_NOISY => 1;
use Inline C => <<'EOC';

SV * my_fmode(SV * handle) {
     int x;
     IO *io;
     io = sv_2io(handle);
     x = IoTYPE(io);
     if (x == IoTYPE_RDONLY) return newSVuv(1);
     if (x == IoTYPE_WRONLY) return newSVuv(2);
     if (x == IoTYPE_RDWR) return newSVuv(3);
     if (x == IoTYPE_APPEND) return newSVuv(4);
     warn("Unable to determine mode\n");
     return 0;
}

EOC

open($fh1, '>', 'test1.txt') or die "Can't open \$fh1: $!";
open($fh2, '>>', 'test2.txt') or die "Can't open \$fh2: $!";

print my_fmode($fh1), " ", my_fmode($fh2), "\n";

close($fh1) or die "Can't close \$fh1: $!";
close($fh2) or die "Can't close \$fh2: $!";
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While this is actually an interesting question, and I appreciate very much salva's answer, I would say that it's not something that would pop up frequently. Indeed in many years I've never felt the need to find out the open mode of a filehandle: generally you're the person who opens it in the first place and thus you do know how to deal with it. Since you claim to be a newbie, I'd be curious as to know what you need this for. After all this may be an XY Problem...

Actually I can think of quite a few use cases for this: in an abstract sense you aren't always the person who opened the file in the first place such as when you are passing a filehandle to a subroutine or method, particularly if the subroutine or method is written by a third party. I'm actually going to have some code that does this in the next release of Term::ReadKey to catch some 'bugs' that seem to crop up on windows.

/J\

Indeed. Though, even if I pass the handle to a sub or method, end even if they're written by someone else, in most cases I do know what they will do with it, i.e. whether they will read from it or write into it. I can imagine situations in which I won't know and I will desire to find out the open mode of the handle, but I would regard them as atypical, especially for a newbie: this is why I asked...