I tried this but I dont think its everything you were talking about: 
#!/usr/bin/perl -w
use URI::Escape;
use HTML::Entities;
use CGI qw/:standard/;
print "Content-type: text/html\n\n";
my $file;
if(param('test')){
        my $code = param('test');
        $code = uri_unescape($code);
        $code = encode_entities($code);
        open STDERR, '>&STDOUT';
                open my $fh, '>', \$file;
                print $fh $code;
                close $fh;
                open my $pipe, '-|', "perl -w $file";
                close $pipe;
        close STDERR;
}

[download]
The output I get with this is: 
sh: -c: line 0: syntax error near unexpected token `;;'
sh: -c: line 0: `perl -w print "hi";'

[download]
This is what is passed to the script: 
print "hi";
print "hello world\n";

[download]

In reply to Re^2: Executing code block in memory by morissette
in thread Executing code block in memory by morissette

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