Here's my aborted attempt at trying to get this to work with parse::recdescent. Currently it doesn't work but maybe someone can supply this missing ingredients. I've got to go back to work ;)

The RecDescent FAQ may be of help for anyone that wants to tinker with this.

#patternInAnotherPattern.pl
use strict;
use warnings;
use Test::More qw(no_plan);
use Parse::RecDescent;

my $str = 'blfoo and barthisfoothatqux and barsofooquxhim andfoosom fo
+o';
my $expected = 'bl123 and barthisfoothatqux and barsofooquxhim and123s
+om 123';
my $parse = Parse::RecDescent->new(q(
    document: chunk(s) /\Z/ { $return = join ('', @{$item[1]}) }
    
    chunk: 
        /./ #just a placeholder, to get the grammar to return somethin
+g, anything!
    
    filler_chunk: 
        /(?!(foo|bar|qux).)*/ #inch ahead
    
    combi_chunk: 
        boundary_chunk foo_chunk boundary_chunk
    
    boundary_chunk: 
        /(bar|qux)((?!foo).)*/ #inch ahead

    foo_chunk: 
        /foo/
        
    bar_chunk:
        /bar/
        
    qux_chunk:
        /qux/
));

my $res = $parse->document($str);
is($res,$expected);
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