In theory you should be able to build for 32bit on a 64bit machine, but it takes a lot of setup :)
Your best bet is setting up a 32bit chroot environment on your machine and install all build tools (gcc, binutils, make etc) there. Also install Perl and all modules you need for you application (and all their build dependencies). Finally install PAR and PAR::Packer and pack your script in this environment.
In place of a 32bit chroot you could also use a 32bit VM - choose what you are already more familiar with. But all of this is about the same amount of work as setting up a real 32bit machine.