use 5.010;  # for (?|pattern) and (*FAIL)

use warnings
    FATAL => 'all'
    ;
use strict;


# factored regexes

my $r_s_g = qr{ (?i) (?> \b (?: revenues? | sales | growth    ) \b) }xms;
my $c_fe  = qr{ (?i) (?> \b (?: currency | foreign \W exchange) \b) }xms;

my $word = qr{ \b \w+ \W+ (?: \b | \Z) }xms;

my $max_between = 4;
my $near = qr{ (?:$word){0,$max_between}? }xms;


# the test text

my $s = <<EOT;
Currency
revenue and sales growth in
foreign exchange Sales and
Revenues
EOT
print qq{[[$s]] \n\n};


# extract matches 'in context'

our @matches;
use re 'eval';
$s =~ m{
    (?=
      (?| ($r_s_g) \W+ $near ($c_fe) | ($c_fe) \W+ $near ($r_s_g))
      (?{ push @matches, [ $1, $2 ] })
      (*FAIL)
    )
  }xmsg;

print qq{'$_->[0]' ... '$_->[1]' \n} for @matches;
print qq{\n};


# just count matches

our $n_matches;
$s =~ m{
    (?=
      (?| $r_s_g \W+ $near $c_fe | $c_fe \W+ $near $r_s_g)
      (?{ ++$n_matches })
      (*FAIL)
    )
  }xmsg;

print qq{$n_matches matches \n};

##</code><code>##

[[Currency
revenue and sales growth in
foreign exchange Sales and
Revenues
]]

'Currency' ... 'revenue'
'Currency' ... 'sales'
'Currency' ... 'growth'
'revenue' ... 'foreign exchange'
'sales' ... 'foreign exchange'
'growth' ... 'foreign exchange'
'foreign exchange' ... 'Sales'
'foreign exchange' ... 'Revenues'

8 matches