$ perl -wMstrict -le 'print unpack("B*",pack("i",3))'
00000011000000000000000000000000
$ perl -wMstrict -le 'print unpack("i",pack("B*",
  "00000011000000000000000000000000"))'
3
$ perl -wMstrict -le 'print unpack("i",pack("B*",
  "00000000000000000000000000000011"))'
50331648
$ perl -wMstrict -le 'print unpack("i",pack("B*","00000011")).""'
Use of uninitialized value in concatenation (.) or string at -e line 1.
$ perl -wMstrict -le 'print unpack("c",pack("B*","00000011"))'
3