re line 8 for windows: perhaps con: or CON: (either appears to work on the rather dated W32 box available right now):

open STDIN, "<", "/con:" or die "Couldn't open console: $!";

To execute a command ^* found in $user_input simply insert

system($user_input);

after line 11 of almut's elegant no-module solution -- which observation is in no way intended to deprecate ikegami's earlier reply using a module which also appears to fit the OP's needs. Both are easily extensible./p>

Update: * ...but this fails with some commands, notably with cd or chdir, although it does "work" with commands like dir or perl -c script.pl.