A quick test with Devel::Peek revealed the following info:

Testscript:
SV = PV(0x176ec4c) at 0x1765288
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,POK,pPOK)
  PV = 0x17601c0 "0.123"\0
  CUR = 5
  LEN = 8
[download]

Original program: 
SV = PVIV(0x1adb6f4) at 0x1b874d8
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,POK,pPOK)
  IV = 0
  PV = 0x1ade30c "83.4"\0
  CUR = 4
  LEN = 8
[download]

Perhaps because it's late at night but, I can't figure out anything else than that the number is interpreted as a string.
But that is odd too, I thought a string would evaluate to zero or the number not int($number) ???

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It's unfair to be an expert.