sub substitute {
 my $message = shift;
 my @numeric_matches = ($message =~ m/\{\\d\d+\}/g);
 foreach (@numeric_matches) {
  my $substitution = $_;
  my ($substitution_count) = (substitution =~ m/(\d+)/);
  my $number;
  for (1..$substitution_count) {
   $number .= $numeric_chars[int rand @numeric_chars];
  }
  $substitution =~ s/\\/\\\\/g;
  $message =~ s/$substitution/$number/ee;
 }
 return $message;
}