Perl claims the right to convert among equivalent representations. It's an optimisation that an UV isn't used unless needed since UVs require extra handling.

>perl -MDevel::Peek -e"Dump(0x7FFFFFFF)"
SV = IV(0x1de9d00) at 0x1de9d04
  REFCNT = 1
  FLAGS = (PADTMP,IOK,READONLY,pIOK)
  IV = 2147483647

>perl -MDevel::Peek -e"Dump(0x80000000)"
SV = IV(0x4a9d00) at 0x4a9d04
  REFCNT = 1
  FLAGS = (PADTMP,IOK,READONLY,pIOK,IsUV)
  UV = 2147483648
[download]