is this because there is a single ' higher in the code?

If your code looks something like this:

my $unterminated_single_quote = '<-- this is not terminated;
use Term::ReadKey; ReadMode('noecho');
$tbpass = ReadLine(0);
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then yes. Single-quoted strings can contain embedded literal newlines (update: i.e., single-quoted strings can be multi-line strings).

Update: Please see Quote and Quote-like Operators and Quote-Like Operators in perlop.