Sorry, I realize my explanation was not clear enough.

Inventory, such as IPs, neighbors, interfaces, etc., is not known in advance. So the Template module not really useful IMO. I want to collect inventory from device configurations, and later import as csv in excel, where simple sort by desired column could outline anomalies. By scanning device configurations against "templates" I make sure that configuration sections are correct, and at the same time acquire inventory.

I wanted this task to b simple for end user, hence no regex in the "template" (or mask) file.

The template example above is transformed in following regex string $mask_tmp:

(mpls ldp)
 (router-id) ([^\n]+)
 nsr
 graceful-restart
 backoff 5 10
 session protection
 (neighbor) ([^\n]+) password encrypted [^\n]+
 (neighbor) ([^\n]+) password encrypted [^\n]+
 (neighbor) ([^\n]+) password encrypted [^\n]+
 igp sync delay 10
 label
  allocate for LLAF
 !
 log
  neighbor
  nsr
 !
 interface ([^\n]+)
 !
 interface ([^\n]+)
 !
 !
[download]

And then I loop (mask can be found multiple times in the configuration) this mask through device configuration stored in $current_cfg as follows:

      while (@MASK_VARIABLES = $current_cfg =~ /$mask_tmp/s) {
         $MASK_VARIABLES = join(",",@MASK_VARIABLES);
         $MASK_SEEN{$hostname}{$mask} = "YES";
         $MASK_COUNT{$hostname}{$mask}++;
         #
         ($MASK_VARIABLES[1] =~ /\w+/) && do {
            print "$hostname,$MASK_VARIABLES\n";
         };
         #
         # remove identified cfg section from router configuration
         #
         $current_cfg =~ s/$mask_tmp//s;
      }
[download]

Result is the following:
- inventories in .csv on stdout (for further analyzing in excel)
- summary view (code not shown above) where I see which and how many times given template has been matched in each device configuration
- remaining of $current_cfg stored in a "leftover" file, where I can see all commands not identifed by above process (this allows network operator to asses any anomalies - ie. config sections not compliant with the template)