$var = 'this is a string\twith some text\r\n';
$var =~ s/\\t/\t/;
$var =~ s/\\r/\r/;
$var =~ s/\\n/\n/;

##</code><code>##

 
$var = 'this is a string\twith some\x09text\r\n';

##</code><code>##

$var =~ s/\\x09/\x09/;