title: How to use regex in Perl to see if a variable has only specific characters?
body: <p>I'd like to use regex in Perl to see if a scalar variable has any characters other than the ones I'm looking for.  The placement or order of the characters don't matter.</p>
  
  <p>For example if want to filter out other than the characters C and F:</p>
  
  <p>Matching to ABCADF would equal true (it has other than my filter characters)</p>
  
  <p>Matching FFC would equal false.</p>
  
  <p>Matching CCCC would also equal false.</p>
  
  <p>Thanks</p>