set asocPattern to current application's NSRegularExpression's regularExpressionWithPattern:"(?i);\\s*charset\\s*=\\s*(\"?)(.+?)\\1\\s*(?:;|$)" options:0 |error|:(missing value) -- sloppy non-RFC1341 pattern not appropriate for general parameter matching, but adequate here as the value will be rejected anyway unless it matches one of the encoding names defined above