C:\Users\Peter>perl -MDevel::Peek -lE "$iv=1<<30; for(1..3) { Dump $iv; $iv<<=1; }" SV = IV(0x68fc28) at 0x68fc2c REFCNT = 1 FLAGS = (IOK,pIOK) IV = 1073741824 SV = IV(0x68fc28) at 0x68fc2c REFCNT = 1 FLAGS = (IOK,pIOK,IsUV) UV = 2147483648 SV = IV(0x68fc28) at 0x68fc2c REFCNT = 1 FLAGS = (IOK,pIOK) IV = 0 C:\Users\Peter>perl -MDevel::Peek -lE "$iv=1<<30; for(1..3) { Dump $iv; $iv*=2; }" SV = IV(0x24dfbe0) at 0x24dfbe4 REFCNT = 1 FLAGS = (IOK,pIOK) IV = 1073741824 SV = IV(0x24dfbe0) at 0x24dfbe4 REFCNT = 1 FLAGS = (IOK,pIOK,IsUV) UV = 2147483648 SV = PVNV(0x7ea464) at 0x24dfbe4 REFCNT = 1 FLAGS = (NOK,pNOK) IV = -2147483648 NV = 4294967296 PV = 0 C:\Users\Peter>perl -V:ivsize ivsize='4';