Interestingly enough, if you change where you are specifying the IO parameters to the open command, it seems to work for all three styles of open commands.

Update: Whoops, edit to restore truncate function, still works though.

Note this was tested under Windows so I changed the cat command, but it is otherwise the same.

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;
      my $op = ($^O =~/MSWin/) ? 'type' : 'cat';
      $test_string eq `$op $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, '>', @_ )          : OK
open( my $fh, '>', @_[ 0..$#_ ] ): OK
open( my $fh, '>', shift, @_ )   : OK

open( my $fh, '>', @_ )          : OK
open( my $fh, '>', @_[ 0..$#_ ] ): OK
open( my $fh, '>', shift, @_ )   : OK
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