use strict;
use warnings;
use feature qw/ say /;
use Scalar::Util qw/ blessed/;

open my $fh, ">", undef;

say blessed( *$fh{ IO });                           # IO::File
say *$fh{ IO }-> can( "print" ) ? "yes" : "no";     # no
autoflush $fh 1;
say *$fh{ IO }-> can( "print" ) ? "yes" : "no";     # yes