I don't like golf that much, but...

use IO::File;

IO::File->new(">$ENV{HOME}/.bash_history") or die "Can't empty history
+: $!\n";
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Since new returns a reference to a filehandle, but because that reference isn't saved, the refcount drops to zero and the file is closed right after opening.

IO::File is included with the distribution, btw

[ ar0n ]