#!/usr/bin/perl

use strict;         # https://perlmonks.org/?node_id=11101749
use warnings;

# "the precise syntax of this configuration file is unknown" <-- FIXME

my $s_in = <<'GROK';
# comment line
VIEW View1
   RECORD           "ABC"
   FIELD            (
      FIELD            "TYPEFROM"
      FIELD            "REGION"
      FIELD            "RUBBISH"
   )
   INTERVAL         600 SECONDS
END_VIEW
VIEW View2
   RECORD           "HELLO"
   FIELD            (
      FIELD            "TYPETO"
      FIELD            "REGION"
      FIELD            "RUBBISH"
   )
   INTERVAL         700 SECONDS
END_VIEW
# random line 1
VIEW View3
   RECORD           "XYZ"
   FIELD            (
      FIELD            "FLD1"
      FIELD            "Region"
# random line 2
      FIELD            "Rubbish"
   )
   INTERVAL         800 SECONDS
END_VIEW
# random line 3
GROK

print $s_in;
print STDERR $s_in =~ s/^VIEW\b.*?^END_VIEW\b/
  my $block = $&;
  $block =~ m{^\h*RECORD\h+"(ABC|XYZ)"}im
    ? $block =~ s!^\h*FIELD\s+\K"REGION"!"LOCATION"!gimr =~
      s!^\h*FIELD\s+\K"RUBBISH"!"TRASH"!gimr
    : $block
  /gemsr;