It receives and prints the @msg lines properly, but then how do I get it to get input from the keyboard again after I'm done reading from the diamond operator?

You just get it:

Windows:

C:\temp>headybrew.pl
foo
bar
baz
^Z
foo
bar
bazWhat do you want to do with this message?wtf
wtf
[download]

*NIX:

wolfgang:~ [21:40:12]$ ./headybrew.pl
foo
bar
baz
foo
bar
bazWhat do you want to do with this message?wtf
wtf
[download]

You just have to pass an end of file to interrupt the first sequence, which happens to be ^Z in the former environment and ^D in the latter. Or did you mean anything else?

Update: apologies, hadn't noticed the $ ls | sillytest, my fault, but perhaps you may have put that in <code> tags too, for maximum visibility.