if( $_ eq "--end foo--\n"){
    # . . .
    }

##</code><code>##

my $interesting_bit;
{
    # maybe open here . . .
    local $/ = '--start foo--' . "\n";
    $interesting_bit = <FILE>;
    local $/ = '--end foo--' . "\n";
    $interesting_bit = <FILE>;
    # . . . and close here
}

##</code><code>##

my $interesting_bit;
{
    # maybe open here . . .
    local $_;
    while (<FILE>) {
        if ($_ eq "--start foo--\n" .. $_ eq "--end foo--\n"  ) {
            $interesting_bit .= $_;
        }
        elsif ( $interesting_bit ) { last }
    }
    # . . . and close
}