Michael Schwern (and others) introduced a new command-line switch, -t, similar to -T, but which turns the taint failures into warnings (in the taint category). This is primarily intended for developers that want to put back a -T in projects that were not designed with -T in mind from the beginning.
Note that this feature is not completely new. You can get the same effect with 5.6.x by using the switches -TUMwarnings=taint. See the docs for why (specifically perlrun/-U).