my $zip = Archive::Zip->new( 'browser.jar' ) || die "$!";

# extract what you want
my $file = "content/browser/browser.js";
$zip->extractMember($file);

# Edit the file as necessary,
# which is at ./content/browser/browser.js

# now add it back
$zip->removeMember($file);
$zip->addFile($file);
$zip->overwrite();