Why does a lexical have the same address

[Scott T. Hildreth]

I have a xsub that has a pointer to a c-structure, and a sv as the
parameters, 

IV
set_fld_name(fld, name)
    
    FLD * fld
    SV  * name
    PREINIT:
        STRLEN len;
    CODE:
        if (name == (SV *)NULL)
            RETVAL = 0;
        else {
            fld->name = SvPV(name, len);
            RETVAL = 1;
        }
    OUTPUT:
        RETVAL


..which changes the name of a 'fld->name'. Which works fine if I only
change one name.  If the sub is called more than once the 'fld->name'
pointers all point to the same string.  The name is a my variable passed
in via a method, so I thought there would be an SV created, but the fld
names changed all point to the same memory, and have the same string.  I
used Devel::Peek to confirm that the address is same.  Here is the
method, 

sub set_name {
    my ($self, $fldnm) = @_;
    my $rc;                 
    my $newself = {};
                     
    $fldnm = lc $fldnm; #== Fmt is case insensitive.
    $rc = fmt_set_fld_name($self->{_ptr}, $fldnm);

.
.
.
     return $newself
 }

 .. so the address of $fldnm is always the same (static).  Therefore the
fld->names that are sent in all point to the same address.  How do I get
a new SV so that the memory area is different. 


                                Thanks,

                                    STH