LogicalChaos,

Ahh but you are incrementing in string land (and integer land is left alone). I missed what operation you used to get to 200 but it probably forced a switch from the PV value to the IV (or maybe NV). Use Devel::Peek to check:

use warnings;
use strict;

use Devel::Peek;

my $v = 99;
print Dump( $v );

$v = sprintf( "%04d", $v );
print "$v\n";
print Dump( $v );

++$v;
print "$v\n";
print Dump( $v );

++$v;
print "$v\n";
print Dump( $v );
[download]

and the output:

SV = IV(0x8101d8c) at 0x8118330
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,IOK,pIOK,IsUV)
  UV = 99
0099
SV = PVIV(0x80f6ba8) at 0x8118330
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,POK,pPOK)
  IV = 99
  PV = 0x8103178 "0099"\0
  CUR = 4
  LEN = 5
0100
SV = PVIV(0x80f6ba8) at 0x8118330
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,POK,pPOK)
  IV = 99
  PV = 0x8103178 "0100"\0
  CUR = 4
  LEN = 5
0101
SV = PVIV(0x80f6ba8) at 0x8118330
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,POK,pPOK)
  IV = 99
  PV = 0x8103178 "0101"\0
  CUR = 4
  LEN = 5
[download]

-derby