G'day andrewkl,

Welcome to the Monastery.

I think you're looking at this back-to-front.

Write your subroutines such that they read the arguments they need. E.g.

sub f {
    my ($AoH) = @_;

    for my $hashref (@$AoH) {
        # do something with $hashref
    }
}
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Then call those subroutines with the appropriate arguments. E.g.

...
# somewhere in your code
f($AoH);
...
# elsewhere in your code
f([$hashref1, $hashref2]);
...
# and at some other point
f([\%hash]);
...
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As you can see from those examples, you can (often) create the argument list in situ.

What you really want to avoid is subroutine definitions like this:

sub g {
    my ($arrayref_containing_just_one_hashref) = @_;
    my $hashref = $arrayref_containing_just_one_hashref->[0];
    # do something with $hashref
}
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So, get the subroutine definition right, then call as needed. If that requires some complex code to create the argument list, so be it.