Check out perldoc -q 'insert a line' (the question in question is in perlfaq5, "How do I change one line in a file/delete a line in a file/insert a line in the middle of a file/append to the beginning of a file?" if the -q doesn't work).

The general idea is that you can't change bytes in the middle of a file unless you are replacing existing data with replacement data that is exactly the same length.

Perl does have a concept of "in-place" editing that can make it appear like you are inserting bytes into the middle of a file, but it's actually rewriting the whole thing...see perldoc perlrun(specifically the -i switch), and perldoc perlvar (the $^I variable).

Here is a little inplace edit script to play with (backup with .bak suffix written):

#!/usr/bin/perl -i.bak -w
@ARGV = ('c:/test.txt');             # set our file to process
while (<>) {
   print "newline\n" if m/somecond/; # add a new line is line matches 
+somecond
   s/this/that/;                     # substitute this for that on eve
+ry line
   print;                            # write the modified (or not) lin
+es
}
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tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

You can make it even simpler:

#!/usr/bin/perl -i.bak -wp c:/test.txt

print "newline\n" if m/somecond/;
s/this/that/;
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IMHO command line switches are a Good Thing (tm).

{news}

Read your whole file into a variable say $page_html and replace:

$page_html =~ s/\{news\}/$news_html/;
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