A combination of both insensate's and Jasper's gems. 

      01  23456789012
perl -pe '$_ x=!$$_++'

[download]

Update: This is, unfortunately, version specific. It works on 5.8 but not on earlier versions. See the short discussion starting with jmcnamara's reply to insensate. Another variation which shouldn't be version specific and which ties Jasper's: 

      01  234567890123456
perl -pe '$_ x=!${_.$_}++'

[download]

-sauoq
"My two cents aren't worth a dime.";

In reply to Re: (Golf) unique (and the winner is...) by sauoq
in thread (Golf) unique by spurperl

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