I see a different problem with dopen

my $x = dopen( 'file-not-found' );
__END__
Can't open `file-not-found': No such file or directory
readline() on closed filehandle $fh
[download]

Ouch. How about this instead:

my $x = dopen( '/dev/null', 'file-not-found', '/etc/passwd' );

sub dopen {
    my @t = map {
        my $fh;
        open $fh, '<', $_ and <$fh> or warn "Can't open `$_': $!\n";
    } @_;
    \@t;
}
__END__
Can't open `/dev/null':
Can't open `file-not-found': No such file or directory
[download]

That has a different problem. It reports an error just because the file happens to be empty.

How about this, then:

my $x = dopen( '/dev/null', 'file-not-found', '/etc/passwd' );

sub dopen {
    my $out = [];
  FILE:
    foreach my $file ( @_ ) {
        my $fh;
        if ( ! open $fh, '<', $file ) {
            warn "Can't read '$file': $!\n";
            next FILE;
        }
        push @{$out}, <$fh>;
    }
    return $out;
}
__END__
Can't read 'file-not-found': No such file or directory
[download]

Looks good! It's readable, it complains at the right times, and it doesn't die when I meant it to warn.

I know this does not answer the question you asked. You seem to be looking for a way to do "sub dopen { [ map { open my $f, '<', $_ or warn "Can't open `$_': $!\n"; <$f> } @_ ] }" without the oh-so-confusing [] hanging around at the outskirts. My point is, that's the least of your problems. Write it so it works and so that someone can understand it.