I have tried with s/text/update/g; all records are updated instead of first record

Why do you think this happened, what do you think needs to change to fix it?

How is the line record that needs to change substitution different from all the other records, what uniquely identifies that one record?

Think about it, say it out loud, write down the answer and share with us

Then visit http://perldoc.perl.org/perlintro.html#More-complex-regular-expressions