There are many, many different ways to approach this and identifying which is simplest is a very subjective measure. Try some of the approaches and see which you think appears simplest to you and just go with that one. TIMTOWTDI.

You could construct a single regex to do a multiline match and replace but that will certainly be far from the simplest approach. I would recommend Apache::Admin::Config over such a complicated approach any day. Note that this is a pure-perl module so you can just use the source if necessary.

However, here's the general all-in-one method:

#!/usr/bin/env perl 
use strict;
use warnings;

my $in = <<EOT;
         <Location />
             MaxConnPerIP 12
             NoIPLimit image/*
         </Location>
EOT
my $max = 16;

my $out = $in;
$out =~ s/(<Location .+?MaxConnPerIP\s+)(?:\d+)(.+?<\/Location>)/$1$ma
+x$2/s;
print $out;
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