/usr/share/doc/libhttp-proxy-perl/examples/flv.pl is in libhttp-proxy-perl 0.300-1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 | #!/usr/bin/perl
use strict;
use warnings;
use HTTP::Proxy;
use HTTP::Proxy::BodyFilter::save;
use Digest::MD5 qw( md5_hex);
use POSIX qw( strftime );
my $proxy = HTTP::Proxy->new(@ARGV);
# a filter to save FLV files somewhere
my $flv_filter = HTTP::Proxy::BodyFilter::save->new(
    filename => sub {
        my ($message) = @_;
        my $uri = $message->request->uri;
        # get the id, or fallback to some md5 hash
        my ($id) = ( $uri->query || '' ) =~ /id=([^&;]+)/i;
        $id = md5_hex($uri) unless $id;
        # compute the filename (including the base site name)
        my ($host) = $uri->host =~ /([^.]+\.[^.]+)$/;
        my $file = strftime "flv/%Y-%m-%d/${host}_$id.flv", localtime;
        # ignore it if we already have it
        return if -e $file && -s $file == $message->content_length;
        # otherwise, save
        return $file;
    },
);
# push the filter for all MIME types we want to catch
for my $mime (qw( video/flv video/x-flv )) {
    $proxy->push_filter(
        mime     => $mime,
        response => $flv_filter,
    );
}
$proxy->start;
 |