Can't, short of making changes to the Perl source.

#define SvREFCNT(sv)     (sv)->sv_refcnt
#define SvREFCNT_inc(sv) ((PL_Sv=MUTABLE_SV(sv)) ? (++(SvREFCNT(PL_Sv)
+),PL_Sv) : NULL)
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As you can see,

SvREFCNT_inc(sv)
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boils down to

++( (sv)->sv_refcnt )
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What's the bigger picture?