@arr = (1, 2, 3, 4, 5);
map {print "** $_ **\n";} @arr;

##</code><code>##

$ast_print = sub {print "** $_[0] **\n"};
process_and_print(25, $ast_print);

sub process_and_print
{
    my $val = $_[0];
    my $print_func= $_[1];

    #..... processing ....

    &$print_func($val);
}

##</code><code>##

$op = "print \"hello\"";
eval $op;

##</code><code>##

while (<>) { eval; print $@; }