You could plan to run all your Perl sources through the C preprocessor before further use and that way co-opt its functionality. The added benefit is that you can then use all of the C preproprocessor functionality, e.g. macros, defined pre-execution symbols and so on in your Perl code - in fact this particular usage pales into triviality compared with what then becomes possible for projects with complex implementation and/or porting requirements.

#!/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__
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