pp_aassign:

tmpstr = NEWSV(29,0);
if (*relem)
    sv_setsv(tmpstr,*relem);
*(relem++) = tmpstr;
didstore = hv_store_ent(hash,sv,tmpstr,0);
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Create new SV, copy stack SV into new SV, set stack element to new SV, store new SV in hash.
hv_store_ent takes ownership of tmpstr; the second time key SV gets set, the first tempstr is dereffed while still on the stack.

I don't immediately see why *(relem++) has to be set to tmpstr.
Other interesting oneliners:

perl -le 'print join ".", %h = (1,2,1,3,1,4)'
1.4.1..1.4

perl -le 'print join ".", %h = (1,2,1,3,1,[])'
1.ARRAY(0x80fa8cc).1.ARRAY(0x80fa8cc).1.ARRAY(0x80fa8cc)
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