Here is my frist try:
It should work for all simple cases like '1234', 121, 12111.0

use Inline 'C';
use Devel::Peek;
my $x;
my $v = 2147483648;
Dump($v);
$x->{T}{z} = force_iv($v);
Dump($x->{T}{z});
__END__
__C__
SV* force_iv(SV*v){
  return SvNOK(v) ? newSVuv(SvNV(v)) : newSVuv(SvIV(v));
}
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