Ah crap, you beat me to it. :)

Update with a fourth sub based on BrowserUK's suggestion. Gets another 2-5% over mine.

Oops, fixed error in u2 that made it look about 10% faster than it was. New timings too.

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/;
              },
} );
__END__
[download]

All unique:
       Rate    u1    u2    u3    u4
u1  15504/s    --  -75%  -95%  -95%
u2  62910/s  306%    --  -78%  -78%
u3 289343/s 1766%  360%    --   -1%
u4 291910/s 1783%  364%    1%    --

Not Unique:
       Rate    u1    u2    u3    u4
u1  17396/s    --  -72%  -98%  -98%
u2  62887/s  262%    --  -92%  -92%
u3 748300/s 4202% 1090%    --   -5%
u4 783739/s 4405% 1146%    5%    --
[download]