Well, the simplest solution is to provide a literal tab character (rather than two characters: backslash and t). Alternatively, you can try to make a tab out of backslash-t with eval.

use strict;
use warnings;

my $t = '\\t';
print "$t:\n";

my $evaled = eval "qq/$t/";
print "$evaled:\n"
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Result:

\t:
    :
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(perlmonks changes literal tab to several spaces, heh)

Than again, maybe eval is more trouble than it's worth. I'd say a hash with all separators that you want to use would work better:

my %seps = (
  '\\t' => "\t",
  '\\n' => "\n",
   # etc
);

my $input = <>;
my $separator = $seps{$input};
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