On reading glob and File::Glob, there seems to be no hard limit on the length of the pattern. There is a possible limit if you call for it explicitly via bsd_glob($pat, GLOB_LIMIT) but this is about the glob expansions and not the argument.

As pointed out in a previous reply, maybe you should avoid the specials of the glob function (like POSIX compliance and split on whitespace) by using bsd_glob directly. Also make some experiments by changing to a directory in Clearcase MVFS directory and expanding a shorter relative path. Maybe it is not working for other reasons, like permissions.