#!/usr/bin/perl
#IFDEF COMMENT
    #+++
    I am a comment - symbol COMMENT is left undefined
    So there
    Instructions: this file is called fred.plp and should
    be run through the C preprocessor with output to fred.pl
    - modules could be presourced with the extension .pmp
    #---
#ENDIF
my $x = 1;
open my $fh, '<fred';
# etc.
__END__