I do not think this is a good idea—you got some already—but it does fulfill the letter of the request. :P

use Math::BigInt;
use Digest::SHA "sha1_hex";

my $string = shift || die "Give a string!\n";
print Math::BigInt->new( "0x" . sha1_hex($string) ), $/;

__END__
"mabye a db would be better"
-> 1118343603570750339537815681476550431532447928026
[download]