Hi vetrivel,

use Math::BigInt lib => "GMP";
This will attempt to use Math::BigInt::GMP, and if Math::BigInt::GMP cannot be found, Math::BigInt will be used instead.

use Math::BigInt::GMP;
This will attempt to use Math::BigInt::GMP, and if Math::BigInt::GMP cannot be found, the program will abort.

In both cases appropriate messages will be output if Math::BigInt::GMP was not found.

Cheers,
Rob