use strict;
use warnings FATAL => 'all';

my @open = (
            q(open( my $fh, @_ )),
            q(open( my $fh, @_[ 0..$#_ ] )),
            q(open( my $fh, shift, @_ )),
           );

my $filename = 'hello_world';
my $test_string = "Hello, world!\n";

for my $prepare ( \&remove, \&truncate ) {

  for my $o ( @open ) {

    my $sub = eval "sub { $o or die \$!; return \$fh }" or
      die 'eval failed';

    $prepare->( $filename );    # remove or truncate

    eval {
      my $fh = $sub->( '>', $filename );
      print $fh $test_string;
      close $fh;
      $test_string eq `cat $filename` or die "incorrect contents\n";
    };

    printf "%-33s: %s", $o, $@ ? $@ : "OK\n";
  }
  print "\n";

}

sub remove {
  unlink shift;
}

sub truncate {
  open my $fh, '>', shift or die $!;
  return;
}
__END__
open( my $fh, @_ )               : No such file or directory at (eval 1) line 1.
open( my $fh, @_[ 0..$#_ ] )     : No such file or directory at (eval 2) line 1.
open( my $fh, shift, @_ )        : OK

open( my $fh, @_ )               : No such file or directory at (eval 5) line 1.
open( my $fh, @_[ 0..$#_ ] )     : Filehandle $fh opened only for input at pita.pl line 25.
open( my $fh, shift, @_ )        : OK