use strict;
use warnings;

my @incoming = (
		"AD\thomas",
		"MAIN\nancy",
		"FOO\randy",
		"nancy",  
	       );  

my %whitespace = (
		  "\n" => "n",
		  "\t" => "t",
		  "\r" => "r",
		  "\f" => "f",
);

for (@incoming) {
  print "$_: ";
  s/(\s)/\\$whitespace{$1}/g;
  print "$_\n";
}