IPC::Run's run basically runs a command to completion, if you want interactive communication with the subprocess, as your code example appears to be showing, you'll want its start/pump/finish interface. The module's documentation is a bit long, but it is a powerful module, so I recommend reading up on it. Also, a more detailed description of what this subprocess is and what you want to communicate to it would be helpful.

Otherwise, if all you want to do is send a single string to its STDIN, then I think you should just be able to do run \@cmd, '<', \$data, ....