CV * T_CVREF
# The Perl core already has a typemap entry for CV*, but empirically the
# one in 5.6 is broken. This is essentially a copy of the one in 5.8,
# which also works for 5.6.
if (SvROK($arg) && SvTYPE(SvRV($arg))==SVt_PVCV)
$var = (CV*)SvRV($arg);
croak(\"$var is not a code reference\")
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