'The guy''s house' is "The guy's house" in perl (well, you could write 'The guy\'s house', too..)
"He said ""Hello""" is "He said \"Hello\"" in perl (or, 'He said "Hello"')

##</code><code>##

#i assume here that you define $comment somewhere else..
$comment =~ s/"/""/g;       # if you use double-quotes
# OR: $comment =~ s/'/''/g; # is you use single-quotes