The addressable data space by a single process under Solaris in 32 bit mode is approximately 3.7GB (yes I know you are running 64 bit Solaris, but my guess is that your perl binary is compiled in 32 bit mode).

Under linux 32 bit (at least the non-Enterprise versions) the limit is just under 2 GB for a single process because of the way linux maps memory. On RH Advanced Server one can use a special kernel variable (mapped_base) to increase the adderssable memory of the process to 2.7GB.

Michael