I used: 
$ perl -i.bak -lne 's/\A\s+//; s/\s+\Z//; next unless $_ and not $seen
+{$_}++; print' input.txt

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And I didn't get empty trailing lines...
[]s, HTH, Massa

In reply to Re^4: Duplicate lines with spaces, tabs... by massa
in thread Duplicate lines with spaces, tabs... by marto9

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