The approach really, really depends on the other system. Will the other "non Perl" system be on the same machine? Will the other system be able to embed Perl (perlembed)? Will the other system be able to talk over a socket or IPC to Perl (perlipc)? Will the other system use some RPC mechanism like SOAP or Web Services? Will it use MQSeries?

Without knowing what the other system supports, it's hard to say which approach to take from Perl.