tr///U was removed in perl 5.6.1 (see my update, and note the upper-case U). perl561delta says:
Support for "tr///CU" and "tr///UC" etc., have been removed since we realized the interface is broken. For similar functionality, see "pack" in perlfunc.
"What should it profit a man, if he should win a flame war, yet lose his cool?"

In reply to Re^2: RFC: perlfeaturedelta by Joost
in thread RFC: perlfeaturedelta by Joost

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