• perlfilter — official documentation
• Filter::Util::Call — the main module
• Filter::Simple — a simplified interface to Filter::Util::Call

Using Filter::Simple without any extra packages

#!/usr/bin/perl

    use strict;
    use warnings;

    use Filter::Simple;
    BEGIN { Filter::Simple::gen_filter_import(__PACKAGE__, sub {
                s/BANG\s+BANG/die 'BANG' if \$BANG/g;
    })->(); }


our $BANG = 1;

BANG     BANG;

Filtering ALL modules

Source filters normally have to be manually loaded into each module, on a case-by-case basis. How do you automatically shove it into every module?

Two tricks needed for this:

• require will respond to a subroutine-ref in @INC, by running that subroutine every time another module does a 'use'
• that subroutine, when it's called, can return

TODO....

Other examples of CPAN modules that do this includes: Acme::use::strict::with::pride, PAR::PAR