use strict;
use warnings;

use Fcntl qw( F_SETFL O_NONBLOCK );

my $fh = \*STDIN;
fcntl($fh, F_SETFL, O_NONBLOCK) || die "$!\n"; 
sysread($fh, my $buf, 1);

##</code><code>##

Your vendor has not defined Fcntl macro F_SETFL, used at ...