$ perl -MDP -we'DHexDump pack "Q", 0x12345678' 0000 78 56 34 12 00 00 00 00 xV4..... $ perl -MDP -we'DHexDump pack "Q>", 0x12345678' 0000 00 00 00 00 12 34 56 78 .....4Vx $ perl -MDP -we'DHexDump pack "Q<", 0x12345678' 0000 78 56 34 12 00 00 00 00 xV4..... $ perl -V:uvsize uvsize='8'; other perl $ perl -V:uvsize uvsize='4'; $ perl -wle'print length pack "Q", 3' Invalid type 'Q' in pack at -e line 1.