#!/usr/bin/perl
# ...
use Some::Third::Party::Module qw( doSomething );
# ...

open my $h,'>:raw','output.bin';
my $oldSelected=select $h;
print "\x00\x42\xAF\x99";
doSomething();
print "\x33\xFF\x81\x73";
select $oldSelected;
close $h;