use Data::Dumper;

$regex = qr<
\b
(?:                                 # Non capturing group

  ## Case 1: currency|foreign exchange comes second
  (revenues?|sales|growth)          # group 1
  \W+
  (?:\w+\W+){0,4}?                  # Non capturing group
  (currency|foreign\Wexchange)      # group 2

  |
  
  ## Case 2: currency|foreign exchange comes first
  (currency|foreign\Wexchange)      # group 3
  \W+
  (?:\w+\W+){0,4}?                  # Non capturing group
  (revenues?|sales|growth)          # group 4
  
)
\b
>x;

$text = <<END_OF_TEXT;
foreign exchange revenue
currency revenue
END_OF_TEXT

print Dumper [ $text =~ /$regex/gi ]