use Math::BigInt;

         # or make it faster: install (optional) Math::BigInt::GMP
         # and always use (it will fall back to pure Perl if the
         # GMP library is not installed):

         use Math::BigInt lib => 'GMP';

         my $str = '1234567890';

         $x = Math::BigInt->new($str);         # defaults to 0
         $y = $x->copy();                      # make a true copy
         $x->badd($y);         # addition (add $y to $x)
         $x->bsub($y);         # subtraction (subtract $y from $x)
         $x->bstr();              # convert to a normalized string
         $x->bsstr();             # normalized string in scientific notation
         $x->as_hex();            # as signed hexadecimal string with prefixed 0x
         $x->as_bin();            # as signed binary string with prefixed 0b

# etc.