use strict;
use warnings;

use Data::Dumper;

use Tie::File;

# open the file if it exists, but fail if it does not exist
use Fcntl 'O_RDWR';

our @array = ();

our $file = 'hai';

tie @array, 'Tie::File', $file, mode => O_RDWR or die $!;

our $SearchString = 'HAI WORLD Times ([0-9]+).*$';
our $ReplaceString = '"\t\t<exML LOLZ = \"" . unpack(\'a1\', $1) . "\"/>"';

my $elementIdx = 0;

while($elementIdx <= $#array)
{
	if($array[$elementIdx] =~ $SearchString)
	{
		# Maintain only the first character
		
		$array[$elementIdx++] = eval $ReplaceString;
	}
	else
	{
		splice @array, $elementIdx, 1;
		# we don't want this in the output
	}
}

untie @array;	# all done!