$ perl -e "printf('%.45f',0.1)"
0.100000000000000005551115123125782702118158340
$ perl -e "printf('%.45f',0.7)"
0.699999999999999955591079014993738383054733276
$ ruby -e "printf('%.45f',0.8)"
0.800000000000000044408920985006261616945266724
$ perl -e "print int((0.1+0.7) * 10)"
7
$ perl -e "print int((0.1+0.7) * 10)"
9
$ perl -v
This is perl, v5.10.1 (*) built for i386-freebsd
...