# Worker function.
sub process_chunk {
    my ($chunk_ref) = @_;

    $$chunk_ref =~ s/[[:punct:]]//g;
    $$chunk_ref =~ s/[0-9]//g;
    $$chunk_ref =~ s/w(as|ere)/be/gi;
    ...

    # Output orderly and serially.
    MCE->relay_lock;
    print $OUT_FH $$chunk_ref; $OUT_FH->flush;
    MCE->relay_unlock;
}