title: Approximate regular expression with a constraint on percentage of errors
body: <p>The approximate regular expression such as the one at <a href="https://pypi.org/project/regex/" rel="nofollow noreferrer">https://pypi.org/project/regex/</a> allows the use of a threshold on the total number of errors (insertions, deletions, substitutions). 
     For example <code>(?:foo){e&lt;=2}</code> allows matches with at most two errors. 
     The threshold here is specified as the total number of errors. Is there any package that allows me to specify <strong>percentage</strong> of errors, instead of total errors? </p>