That's not interactive, that's taking the source code via STDIN. There's a difference, namely in that interactive means you run one command, get the return value. Run another, get another return value. This is commonly known as REPL, or a Read Eval Print Loop. You can make one in Perl:

  perl -le '@ret = eval and print "Returned [@ret]" while <STDIN>'
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But it's not quite as fully featured as most interactive shells.