This is your actual program:

open( FH, "+>toc1.ncx" );
$OH1 = select(FH);
open( FILE, 'b.txt' ) or die "$!";
while (<FILE>) {
    if (
m/^(ISBN Number|book title|Cover|Half|Title|Copyright|Content|Preface)
+:(.*)/
      )
    {
        push( @arr, $2 );
    }
}
[download]

Your print statement will never execute as it was turned into a comment.

So what is your question? Assume we know nothing about ".ncx"-files.

Some very preliminary comments are:

1. You are not using "use strict; use warnings;
2. You are using two argument open rather than the three argument version.
3. You are not using lexical filehandles.
4. "Kidnapping" the standard out filehandle and pointing it to a file is probably a bad idea. It is better to use an explicit filehandle in your print-statements.