I just played around with it using Devel::Peek to see what the values in the sequence are

Good idea - and checking with Devel::Peek::Dump() shows up another anomaly:

C:\_32>perl -MDevel::Peek -le "@x=('0' .. '2'); Dump $x[0];"
SV = PV(0x54c658) at 0x54bc28
  REFCNT = 1
  FLAGS = (POK,pPOK)
  PV = 0x548438 "0"\0
  CUR = 1
  LEN = 10

C:\_32>perl -MDevel::Peek -le "@x=('1' .. '2'); Dump $x[0];"
SV = IV(0x31bc18) at 0x31bc28
  REFCNT = 1
  FLAGS = (IOK,pIOK)
  IV = 1
[download]

It appears that something being done by the range operator changes the PV '1' to an IV, but leaves the string '0' as a PV.
I wouldn't be surprised if this different treatment is causally related to the unexpected behaviour being exhibited.

Cheers,
Rob