http://www.perlmonks.org?node_id=646871

pysome has asked for the wisdom of the Perl Monks concerning the following question:

Hi All,
I wanna add some text to a file in its fixed position.Say the line 3. How to achieve? That is , if the file(a.txt) like:
ab
cd
ef
ghij
klmn
I wanna add "a test content\n" after the "ef".My ideal result is :
ab
cd
ef
a test content
<blank line>
ghij
klmn