Sometimes verbose code is faster. This beat out the above regexp examples in all the cases I threw at it. (NOTE: the "Note unique" example is a best case scenario for this example, but the worst case of "All unique" still performs better"). 
use Benchmark qw( cmpthese ) ;

my $digits = 2491306578;

cmpthese( -5, {
  u1 => sub{
         for ( 0 .. 9 ) { return 0 if $digits !~ /$_/;} return 1;
           },

  u2 => sub{
          my @x = sort split //, $digits;
          my $x = join "", @x; 
          $x =~ tr/0-9//s;
          length $x == 10 ? return 1 : return 0;
            },

  u3 => sub {
          return 0 if $digits =~ /(\d).*\1/; return 1;
            },

  u4 => sub {
          return $digits !~ /(.).*\1/;
            },

  u9 => sub {
          return 0 if index($digits, substr($digits,0,1), 1) != -1; 
          return 0 if index($digits, substr($digits,1,1), 2) != -1; 
          return 0 if index($digits, substr($digits,2,1), 3) != -1; 
          return 0 if index($digits, substr($digits,3,1), 4) != -1; 
          return 0 if index($digits, substr($digits,4,1), 5) != -1; 
          return 0 if index($digits, substr($digits,5,1), 6) != -1; 
          return 0 if index($digits, substr($digits,6,1), 7) != -1; 
          return 0 if index($digits, substr($digits,7,1), 8) != -1; 
          return 0 if index($digits, substr($digits,8,1), 9) != -1; 
          return 1;
            },

} );
__END__

[download]
All unique (2491306578):
       Rate    u1    u2    u3    u4    u9
u1  14387/s    --  -71%  -91%  -91%  -93%
u2  50142/s  249%    --  -67%  -67%  -74%
u3 153182/s  965%  205%    --   -0%  -22%
u4 153395/s  966%  206%    0%    --  -22%
u9 195811/s 1261%  291%   28%   28%    --

Not unique (1102345678):
        Rate     u1     u2     u3     u4     u9
u1   14381/s     --   -71%   -97%   -97%   -99%
u2   50429/s   251%     --   -91%   -91%   -97%
u3  531431/s  3595%   954%     --    -4%   -65%
u4  556425/s  3769%  1003%     5%     --   -64%
u9 1539566/s 10606%  2953%   190%   177%     --

[download]

In reply to Re: Determining uniqueness in a string. by rtst
in thread Determining uniqueness in a string. by Yzzyx

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