Here's an alternative way of writing the function that might be clearer.

SV* new(const char * classname, const char * name, const char * rank, 
+long serial) {
    Soldier * soldier;
    SV      * obj;
    SV      * obj_ref;

    New(42, soldier, 1, Soldier);
    soldier->name = savepv(name);
    soldier->rank = savepv(rank);
    soldier->serial = serial;

    obj = newSViv((IV)soldier);
    obj_ref = newRV_noinc(obj);
    sv_bless(obj_ref, gv_stashpv(classname, GV_ADD));
    SvREADONLY_on(obj);

    return obj_ref;  // Inline will mortalize.
}
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