while (<FILE>) {
     $count += () = m/foo/g
}
print $count;

##</code><code>##

while (<FILE>) {
    while (/foo/g) {
        $count++;
        print "$count so far.\n";
    }
}

##</code><code>##

my $count;
while (<FILE>) {
   if ( $count += s/foo/foo/g ) { print "$count so far\n" )
}