open my $fhout, '>', "./test_out.file" or die "$!";

##</code><code>##

open (my $fhout, '>', "./test_out.file") || die "$!";

##</code><code>##

open (my $fhout, '>', ("./test_out.file" || die "$!"));

##</code><code>##

my ($fhout) = @_;

##</code><code>##

my $fhout = shift;