The regular expression: (?x-ims: \b (MODULE \s+ [A-Z]+[0-9]+) \s* [(] .+? [)] ) matches as follows: NODE EXPLANATION ---------------------------------------------------------------------- (?x-ims: group, but do not capture (disregarding whitespace and comments) (case-sensitive) (with ^ and $ matching normally) (with . not matching \n): ---------------------------------------------------------------------- \b the boundary between a word char (\w) and something that is not a word char ---------------------------------------------------------------------- ( group and capture to \1: ---------------------------------------------------------------------- MODULE 'MODULE' ---------------------------------------------------------------------- \s+ whitespace (\n, \r, \t, \f, and " ") (1 or more times (matching the most amount possible)) ---------------------------------------------------------------------- [A-Z]+ any character of: 'A' to 'Z' (1 or more times (matching the most amount possible)) ---------------------------------------------------------------------- [0-9]+ any character of: '0' to '9' (1 or more times (matching the most amount possible)) ---------------------------------------------------------------------- ) end of \1 ---------------------------------------------------------------------- \s* whitespace (\n, \r, \t, \f, and " ") (0 or more times (matching the most amount possible)) ---------------------------------------------------------------------- [(] any character of: '(' ---------------------------------------------------------------------- .+? any character except \n (1 or more times (matching the least amount possible)) ---------------------------------------------------------------------- [)] any character of: ')' ---------------------------------------------------------------------- ) end of grouping ----------------------------------------------------------------------