do [$fh, sub {s/s/ss/gs; s/([\nS])/$1$1$1/gs; return;}] or die;

##</code><code>##

unshift @INC, sub {
    no warnings 'uninitialized';
    ref $_[1] eq 'ARRAY' ? @{$_[1]} : $_[1];
};

##</code><code>##

open $fh, "<", \<<'EOC';
BEGIN {prepend_block_counting_filter};
pas("SSS make s fast SSS");
EOC

##</code><code>##

open file handles to "in memory" files held in Perl scalars via:

    open($fh, ’>’, \$variable)