title: Detect exact string value of scalar in regex matching
body: <p>Say I have <code>$foo = "bar.baz"</code> </p>
  
  <p>I want to use the scalar $foo to find strings that contain "bar.baz" (anywhere in the string), but not the regex-evaluted version of $foo. </p>
  
  <p>So the line: <code>if( $other =~ m/$foo/ ) ...</code> 
  isn't working, because $foo is being evaluated such that the '.' is evaluated to any character. How do I stop that?</p>