line1
        line2

##</code><code>##

    a   line1
    a       line2

##</code><code>##

  DB<8> y caller_id assertion report_code
$assertion = '$x < \'1\''
$caller_id = 1
$report_code = " unless(\$x < '1') {\cI\cI\cI\cI\cI\cI\cI\cI  \cISmart::Comments::Any::Warn_for( \cI\cI\cI\cI\cI\cI\cI\cI\cI\cI \cI\cI\cI1, \cI\cI\cI\cI\cI\cI\cI\cI  \cI\cI\"\\n\", \cI\cI\cI\cI\cI\cI\cI\cI\cI\cI \cI\cI\cIq{### \$x < '1' was not true} \cI\cI\cI\cI \cI\cI);\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI  \cI Smart::Comments::Any::Dump_for(\cI\cI\cI\cI\cI\cI\cI  \cI-caller_id\cI=> 1,\cI\cI  \cI-prefix\cI\cI=> q{    \$x was:},\cI  \cI-varref\cI\cI=> [\$x], \cI\cI\cI  \cI-no_newline\cI=> 1\cI\cI\cI\cI  );\cI\cI\cI\cI\cI\cI\cI\cI\cI;\cI\cI\cI\cI\cI\cI\cI  \cI die \"\\n\"\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI  }\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI\cI"

##</code><code>##

# --- TAB STOPS ---                     1   1   1   1   1   1   1   1   1   1#
#   1   2   3   4   5   6   7   8   9   0   1   2   3   4   5   6   7   8   9#
#   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |#

##</code><code>##

 1: # This is not a subroutine but a call to Filter::Simple::FILTER
 2: #   with its single argument being its following block. 
 3: # 
 4: FILTER {
 5:     ##### |--- Start of filter ---|
 6:     ##### @_
 7:     
 8:     # Assertions...
 9:     s{ ^ $hws* $intro [ \t] $check : \s* (.*?) $optcolon $hws* $ }
10:      { _decode_assert($caller_id, $1) }egmx;
11:     
12: # Undocumented feature:
13: #    # Anything else is a literal string...
14: #    s{ ^ $hws* $intro $hws* (.*) }
15: #     {Dump_for(-prefix=>q{$1});$DBX}gmx;
16:     
17: #~ say "---| Source after filtering:\n", $_, '|--- END SOURCE CODE';        #~
18:     
19: };
20: