#!/usr/bin/env perl

# Execute shell commands and include their output in the current buffer.
#
# See also: filter-exec for formatted output including the original command.

use strict;
use warnings;
use 5.10.0;

my $text;
{
  # line separator:
  local $/ = undef;
  $text = <>;
}

$text =~ s{
  <!--[ ]exec-raw[ ](.*?)[ ]-->
  .*?
  <!--[ ]end[ ]-->
}{
  handle_block($1);
}egsx;

print $text;

sub handle_block {
  my ($command) = @_;
  my $result = `$command`;
  my $starter = 'exec-raw';
  return "<!-- $starter $command -->\n$result<!-- end -->";
}

__DATA__
A self-test - use ,r in vim to check:

<!-- exec-raw date -->
Mon Oct 31 16:54:45 MDT 2016
<!-- end -->

<!-- exec-raw pwd -->
/home/brennen/code/bpb-kit
<!-- end -->

<!-- exec -->

    $ ls
    apache2
    bpb-kit_1.0_all.deb
    home
    install.sh
    ns-control
    README.md
    tags

<!-- end -->