If you eval a string containing a named sub definition, it gets installed into the current package:

c:\test>perl -E"eval 'sub Foo{ return 12345 }'; print Foo();"
12345
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If you want to create an anonymous sub and get a reference to it into a variable:

c:\test>perl -E"$f = eval 'sub { return 12345 }'; print $f->();"
12345

c:\test>perl -E"$f = eval 'sub { return "bar" }'; print $f->();"
bar
[download]

That works also.

Thank you, I thought I need to use something called "dynloader" from core which is used by source filters but this happened to be more easier that I could imagine :-)

I got my second Perl experiment to work exactly the way I wanted by using this anonymous sub reference solution.

Here is my extremely fast precompiled Embedded Perl HTML template for your reference.

use 5.010;
use strict;
use warnings;

our $start_time = time;

#Embedded perl HTML template compiler object class
package HTML::template;

#Preloads new template object: 
#@_ = class, embedded perl/html input source
sub new
{    
    my ($class, $input) = @_;
    $input //= $_;

    #Slurp the source template
    open my $fh, "<", $input or die "$! \"$input\"";
    local $/;
    my $slurp = <$fh>;
    close $fh;

    #Extract perl script from the template
    my $content = \$slurp;
    my $position = 0;
    my $script = "sub {\n\# line 1 \"$input\"\n";

    #Scan html comment tags
    while ( $slurp =~ /<!--(?<cmd>.*?)-->/gso )
    {
        #Insert text block
        $script .= "print substr(\${\$content},$position,$-[0]-$positi
+on);\n";
        #Translate line numbers
        my $line = ( substr($slurp,0,$position) =~ tr/\n// ) + 1;
        #Insert perl block using fixed line number
        $script .= "\# line $line\n$+{cmd}\n";
        #Advance to next block
        $position = $+[0];
    }    
    #Insert the last text block
    $script .= "print substr(\${\$content},$position);}";

    #Precompile script
    my $compiled = eval($script) or die;

    #Define template object list
    bless [$content, $compiled], $class;
}

#Execute the template object
##@_ = class, html output target
sub run
{
    my ($self, $output) = @_;
    my ($content, $compiled) = @{$self};
    $output //= $_;
    #Redirect output
    local (*STDOUT);
    open(STDOUT, ">", $output);
    #Excute precompiled script
    $compiled->();
}

#Sample program utilizing HTML::template
my $sample_input = <<'END';
Numbers generated at <!--print $start_time;--><br>
<!--for(my $x = 1; $x < 5; $x++) {-->Number=<!--print $x;--><br>
<!--}-->Time used <!--print time - $start_time;--> seconds.<br>
END

my $template = HTML::template->new(\$sample_input);
my $sample_output = '';
$template->run(\$sample_output);
print $sample_output;

#Output from sample_template
Numbers generated at 1265498059<br>
Number=1<br>
Number=2<br>
Number=3<br>
Number=4<br>
Time used 0 seconds.<br>
[download]

Perl code + Template = Text::Template


use warnings;
use strict;

use Text::Template qw(fill_in_string);

print fill_in_string(<<'EOT');
Numbers generated at { $start_time = time }<br>{
  for my $x (1 .. 4) {
    $OUT .= "\nNumber=$x<br>"
  }
}
Time used { time - $start_time } seconds.<br>
EOT
[download]

Its been done before Template, HTML::Mason, HTML::Embperl

eval "sub foo { return 'bar'; } ; 1";
warn 'foo'->();
__END__
bar at - line 2.
[download]