However, when I try and run this piece of code I come up with a message stating:

"Undefined subroutine &model::MAKE_BASIS::inheir_merge"

Well, that's because this is a subroutine call:

$RULES  = inheir_merge(
                exports => {
# Environment variables to export at program's runtime.
                },
                opts => {
# A hash of options that get passed into a program.
                },
# Time limit for execution
                timeout         =>      12
);
[download]

and perl can't find a subroutine like

sub inheir_merge {
    # subroutine code here
}
[download]

in the package model::MAKE_BASIS. Do you have that subroutine in a file you didn't post (model/MAKE_BASIS.pm) ? what is it supposed to do?

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}