If you:
opendir(ims, ...
your dir handle is "ims", as in 'readdir ims'. The grep is to remove unix files . and .. the current and parent dir links. readdir returns just the filenames, not the whole path, so your chdir will work, but so should his prepend of the path, as in (perldoc -f readdir):

   opendir(DIR, $some_dir) || die "can't opendir $some_dir: $!";
   @dots = grep { /^\./ && -f "$some_dir/$_" } readdir(DIR);
   closedir DIR;
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