When you ask a question, the monks are happy to see your effort in the shape of the code you tried before asking for help. But when you're confused about how to write down the algorithm or the program or about Perl itself, it could help a prose description of what you're trying to do. Sometimes you'll be surprised about how people may offer simpler solutions you haven't thought about it.

Well, after this unsolicited introduction, I am not sure what you're trying to do. Maybe replacing literal escape sequences like '\n' with their meaning "\n", which could be done with code like

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

Or maybe you're trying to do the opposite: turn newlines ("\n"), tabs ("\t") into escapes ('\n', '\t'). Where something like this might work

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

But you may find useful a ready-to-use module like Text::Quote as well.