Nice, but it only works with bar then foo then qux, not qux then foo then bar. (Following passes first test, fails second test.) 
use strict;
use warnings;
use Test::More qw(no_plan);

my $str = 'blfoo and barthisfoothatqux and barsofooquxhim andfoosom fo
+o';
my $expected = 'bl123 and barthisfoothatqux and barsofooquxhim and123s
+om 123';
$str =~ s[(bar.+?qux)|(foo)][defined $2 ? '123' : $1]xge; 
is($str,$expected);

#switch qux and bar
$str = 'blfoo and quxthisfoothatbar and barsofooquxhim andfoosom foo';
$expected = 'bl123 and barthisfoothatqux and barsofooquxhim and123som 
+123';
$str =~ s[(bar.+?qux)|(foo)][defined $2 ? '123' : $1]xge; 
is($str,$expected);

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I'm trying to solve the more "general" problem with parse::recdescent, further on in the thread. I gave up before finding a solution though.

In reply to Re^2: Match a pattern only if it is not within another pattern by tphyahoo
in thread Match a pattern only if it is not within another pattern by punkish

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