package Extra;

use Symbol;

sub open
{
    my ( $fh, $direction, $filename ) = @_;
    
    $$fh = Symbol::gensym;
    open ( $$fh, $direction, $filename );
}

1;
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I think this should work without explicit references:

sub open
{
    my (undef, $direction, $filename)=@_;

    $_[0]=Symbol::gensym;
    open ($_[0],$direction,$filename);
}
[download]

The trick is not to copy the alias in @_, but to directly use the alias. Maybe you need to extend open to have a prototype of ($$$).

Anyway, I would prefer a modified open function to return a handle or undef instead of a boolean, so:

sub open
{
    my ($direction,$filename)=@_;
    open my $h,$direction,$filename or return;
    # alternatively: or die "Can't open $filename: $!";
    return $h;
}
[download]

Alexander