perl -MYAPE::Regex::Explain -E 'say YAPE::Regex::Explain->new(q/@{[s".."."gr]}\K$"/)->explain' #### The regular expression: (?-imsx:@{[s".."."gr]}\K$") matches as follows: NODE EXPLANATION ---------------------------------------------------------------------- (?-imsx: group, but do not capture (case-sensitive) (with ^ and $ matching normally) (with . not matching \n) (matching whitespace and # normally): ---------------------------------------------------------------------- @{ '@{' ---------------------------------------------------------------------- [s".."."gr] any character of: 's', '"', '.', '.', '"', '.', '"', 'g', 'r' ---------------------------------------------------------------------- } '}' ---------------------------------------------------------------------- \K 'K' ---------------------------------------------------------------------- $ before an optional \n, and the end of the string ---------------------------------------------------------------------- " '"' ---------------------------------------------------------------------- ) end of grouping ----------------------------------------------------------------------