"Not tested" is, perhaps, a very kind way of putting it. You may have intended to match both the filename and the PID, but you failed to do the latter anywhere in the code. In addition, you're comparing '$c_file' against a non-existent variable called '$input_string'. Last of all, even if you had checked both the filename and the PID against reasonable values, you'd continue to print lines until you had another successful match - which may not be the right thing to do.

Update Modified phrasing.