Depending on your OS, you may not have "\n" in your data at all: it might be "\r\f" (CR-LF) instead (or, rarely, something else). Try:

my @foo = split "\n|\r\f", $test;
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Also, my ($test) = @ARGV will put only the first element of @ARGV (that is, $ARGV[0]) in $test. Is that what you wanted?

To help debug what you've got, try this:

$test =~ s/\n/**/g; ## replace all \n with '**'
$test =~ s/\r/!!/g; ## replace all \r with '!!'
print STDERR qq/'$test'/;
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If you still can't figure out what's wrong, paste the output from that, so maybe one of us will see something you're missing.