Right, use re 'taint'; doesn't appear to do anything useful:

$ perl -e 'use re "taint"; open FH, pop; close FH;' ">somefile"
$ perl -T -e 'open FH, pop; close FH;' ">somefile"
Insecure dependency in open while running with -T switch at -e line 1.
$ perl -v

This is perl, v5.8.2 built for i686-linux
 . . .
[download]

It's purpose is basically so you can have the orthagonal operation, no re 'taint';, which is useful (sort of . . . ).