This piece is as much an aide de memoire for myself as anything else but putting it here seems worthwhile if it answers questions for others. The binding operators, =~ or !~, come in handy when you are framing conditional statements in Perl using Regular Expressions, for example, testing whether x =~ /\d+/ or not. The =~ variant is also used for changing strings using the s/[pattern1]/[pattern2]/ regexp construct (the “s” stands for “substitute”). What has brought this to mind is that I wanted to ensure that something was done for strings that did not contain a certain pattern and that’s where the !~ binding operator came in useful; ^~ might have come to mind for some reason but it wasn’t what I needed.