my $re = qr/
  \b event \s* = \s* "  # Match word boundary, "event", 
                        # optional space, "=", optional
                        # space, and a double-quote.
  ( [^"(]+ )            # Capture any quantity of anything
                        # that is not a double-quote or an
                        # open paren.
  ["(]                  # Anchor to another double-quote or
                        # an opening paren.
/x;                     # Extended pattern (literal whitespace
                        # and comments aren't significant).

if( $match =~ $re ) {
  print "Captured: [[$1]]]]";
}