in reply to
Re^2: How can I replace a line (tag) in an XML file?
in thread How can I replace a line (tag) in an XML file?
You update the initial file the same way you would update a text file, or any other type of file: in this case once you've read the file close it, then open in for writing ans print the output to this filehandle.
The way you use open, the fact that you use sysread are kind of unusual, so either you have a very personal style or you have little Perl experience and you are cargo-culting your way through the problem. You may want to read a little bit about Perl if you need to use it properly. Invest in "Learning Perl", or read the docs (at least the part on open and print, type perldoc -f open to get them