#!/usr/bin/env perl

use strict;
use warnings;

my $sep = '=' x 60 . "\n";
(my $dh_file = $0) =~ s/pl$/dat/;
open_dh($dh_file);

while (1) {
    print 'Get next DH record (y/n): ';
    my $reply = <>;
    if ($reply =~ /^y/i) {
        print "Next DH record:\n";
        my $dh_record = read_dh();
        print "$sep$dh_record\n$sep";

        if (eof_dh()) {
            print "No more DH records!\n";
            last;
        } 
    }
    else {
        print "Stopped reading DH records.\n";
        last;
    }
}

close_dh();

{
    my $dh_fh;

    sub open_dh {
        my $dh_file = shift;
        open $dh_fh, '<', $dh_file or die "Can't read $dh_file: $!";
        my $discard = read_dh(); 
        return;
    }

    sub read_dh {
        local $/ = 'DH: ';
        my $dh_trim_re = qr{\A \s* (.*?) \s* (?: DH: \s )? \z}msx;
        my $dh_record = <$dh_fh>;
        $dh_record =~ s/$dh_trim_re/$1/;
        return $dh_record;
    }

    sub close_dh {
        close $dh_fh;
        return;
    }

    sub eof_dh {
        return eof $dh_fh;
    } 
}