#!/usr/bin/perl

use warnings;
use strict;

# if the argument to die ends with newline, die
# won't print the line number:
# open (READ, "test.xml") || die "ERROR: $!\n";

# you probably want to know which file the error
# relates to and the mode (read or write):
open READ, "< test.xml" or die "ERROR opening test.xml for reading: $!";
# NOTE that we use 'or', a lower-precedence logical
# operator so that we can leave off the parentheses
# around the arguments to open()

my @array = <READ>;

# close can fail. if it does, you probably want to know
# about it:
close READ or die "ERROR closing READ filehandle: $!";

# see above comments
# open (WRITE, ">new.xml") || die "ERROR: $!\n"; 
open WRITE, "> new.xml" or die "ERROR creating new.xml: $!"; 

# make WRITE the default filehandle
select WRITE;

foreach (@array) {
    # '<' and '!' are not meta-characters so there's no
    # need to escape them:
    if (/<!-- Testing XML -->/) {
        # use a here-document (see the perlop man page)
        print <<_EOF_;
<bar>
<name> TEST </name>
<type> Foo </type>
<!-- PDP Status -->
<unknown_sec> 0 </unknown_sec>
</bar>

_EOF_
    }
    # in /PATTERN/, the '/' character is your delimiter.
    # if the pattern delimiter occurs in the pattern,
    # instead of escaping the delimiter, use a different
    # delimiter with the explicit m operator. here we
    # use '!' as our delimiter:
    if (m!</ Test Tag>!) {
        print "<bar><value> TEST </value></bar>\n";
    }
    # \n$ : this is redundant. the $ anchor matches an optional newline
    if (m!</v></row>$!) {
        # note the use of '@' instead of '/' as the delimiter:
        s@</row>$@@;
        $_ .= "<v> UnKnown </v></row>\n";
        print;      # prints $_ by default
    }
    else {
        print;
    }
}

close WRITE or die "ERROR closing WRITE filehandle: $!";