I will try to explain better.

#main script

...

...  #i am doing something

system ("perl eck.pl $var > file.txt &"); #here i call my other script and i redirect the output into the file.txt. My eck.pl script will run some time but in my master script i need to use the newly added lines (always) from the txt file

I need to read that file always ...i can do that but the problem is that is blocking my main script and i can;t use the new lines in my master script. In a way i am trying to read that file "live" get the lines and use them inside my master script.

Hope you understand what i am trying to say.