#!/usr/bin/perl

use strict;

print qq{<?xml version="1.0"?>\n};
my $tag;

while(<DATA>) {
    chomp;
    if ( /^\[(\w+)\]/ ... /^\w+/ ) {
        $tag = $1 if $1;
        print "<$tag>$_</$tag>\n" if ( ! /^\[/ );
    }
}

__DATA__
[DATA]
data1
[ENTRY]
entrying here
[STORY]
story details