#!/usr/bin/perl
use warnings;
use strict;

my $string = 'd"alice';

{
    use re 'debug';

    open STDERR, '>', 'err.txt' or die $!;
    open STDOUT, '>', 'out.txt' or die $!;

    $string =~ s/\bd\"//g;
}

$string =~ /alice/;

##</code><code>##

$ ./bound.pl 
Compiling REx "\bd\%""
Final program:
   1: BOUND (2)
   2: EXACT <d"> (4)
   4: END (0)
anchored "d%"" at 0 (checking anchored) stclass BOUND minlen 2 

##</code><code>##

Compiling REx "\bd\%""
Final program:
   1: BOUND (2)
   2: EXACT <d"> (4)
   4: END (0)
anchored "d%"" at 0 (checking anchored) stclass BOUND minlen 2 
Matching REx "\bd\%"" against "d%"alice"
Intuit: trying to determine minimum start position...
  doing 'check' fbm scan, [0..7] gave 0
  Found anchored substr "d%"" at offset 0 (rx_origin now 0)...
  (multiline anchor test skipped)
  looking for class: start_shift: 0 check_at: 0 rx_origin: 0 endpos: 1
  Does not contradict STCLASS...
Intuit: Successfully guessed: match at offset 0
   0 <> <d"alice>            |  1:BOUND(2)
   0 <> <d"alice>            |  2:EXACT <d">(4)
   2 <d"> <alice>            |  4:END(0)
Match successful!
Matching REx "\bd\%"" against "alice"
Intuit: trying to determine minimum start position...
  doing 'check' fbm scan, [2..7] gave -1
  Did not find anchored substr "d%""...
Match rejected by optimizer
Freeing REx: "\bd\%""