atomo's regexp flags

gistfile1.hs

-- standard Perl
toOpt 'm' = return compMultiline
toOpt 's' = return compDotAll
toOpt 'i' = return compCaseless
toOpt 'x' = return compExtended

-- additional
toOpt 'a' = return compAnchored
toOpt 'G' = return compUngreedy
toOpt 'e' = return compDollarEndOnly
toOpt 'f' = return compFirstLine
toOpt 'C' = return compNoAutoCapture

toOpt c = fail $ "unknown regex flag " ++ show c