use strict; 
use warnings;
use Fcntl qw(F_GETFL F_SETFL O_NONBLOCK);

my $file_name='/tmp/test_me.txt';

open my $fh,'>',$file_name || die "can't open $file_name for writing: $!\n";
my $flags=fcntl $fh,F_GETFL,O_NONBLOCK || die "fcntl call failed: $!\n";
print "Flags: $flags\n";
close $fh || die "can't close write handle to $file_name: $!\n";

##</code><code>##

my $flags=fcntl(FH,F_GETFL,$_) || die "fcntl call failed: $!\n";