use Benchmark qw[cmpthese];

sub one {
        sprintf("%09d",@_);
}

sub two {
        substr("000000000$_[0]",-9);
}

cmpthese(100, {
        one => sub { for(0..10000) { $_ = one($_) } },
        two => sub { for(0..10000) { $_ = two($_) } },
        tre => sub { for(0..10000) { $_ = sprintf("%09d", $_) } },
});

__DATA__
Benchmark: timing 100 iterations of one, tre, two...
       one: 12 wallclock secs (10.63 usr +  0.00 sys = 10.63 CPU) @  9.41/s (n=100)
       tre:  3 wallclock secs ( 3.38 usr +  0.00 sys =  3.38 CPU) @ 29.59/s (n=100)
       two: 12 wallclock secs (11.08 usr +  0.00 sys = 11.08 CPU) @  9.03/s (n=100)
      Rate  two  one  tre
two 9.03/s   --  -4% -69%
one 9.41/s   4%   -- -68%
tre 29.6/s 228% 214%   --