my %map = ( '\n' => "\n", '\t' => "\t" );
$_ = "whatever";
s/(\\[ntf\\])/$map{$1}||'?'/g

##</code><code>##

my %imap = ( "\n" => '\n', "\t" => '\t' );
my $specials = join '|', keys %imap;
$_ = "a\nb\tcksl";
s/($specials)/$imap{$1}/gms;