use strict;
use warnings;
use Math::BigInt;

my $string = '12349' x 10;
my $x = Math::BigInt->new($string);
print  $x,  "\n"; # $x is a Math::BigInt object
$x++;
print "$x", "\n"; # "$x" is a string

__END__
Outputs:
12349123491234912349123491234912349123491234912349
12349123491234912349123491234912349123491234912350