just replace it

$x = '\n';
$x =~ s/(?<!\\)\\n/\n/g;
print $x;
[download]

Update: Well, I was first but I had to pay my price :) - as suaveant correctly pointed out, you have to take care of the special case of an escaped escape so I fixed that.

What would be interesting is a simple general solution which does that transformation not only for \n but also \t, \cC, \xFF, ... but I'm lost there. Anybody??

-- Hofmator