Whatever convention you use: use it, as long as it is good for you. It is good for anybody else too, if it's documented. But be consistent.

That said, I have the same uneasieness with splitting up $blivet into variables with a pre- or postfix as I have when I see $var_1, $var_2, $var_3 instead of @var.

If you have a thingy which is this or that depending on context and/or has some attributes associated, use a suitable container for them. This can be a hash or an object.

So, I'd rather say:

$blivet->file_name;
$blivet->file_rel;
$blivet->file_abs;
# and so on
[download]

Concatenating a identifier with a functional part - i.e. some kind of index - into a new identifier just looks wrong to me.