The definition of "absolute" just means it starts with a slash. Some people refer to your intended result as a "canonical" path, and removing all backtracking as the "canonicalization" of a path. There are other elements to canonicalization, such as discovering aliased mount points or symlinks.

Perhaps something like this will work for you.

1 while ($path =~ s{ [^/]+ / \.\. / }{}x);
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