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

    for my $hashref (@$AoH) {
        # do something with $hashref
    }
}

##</code><code>##

...
# somewhere in your code
f($AoH);
...
# elsewhere in your code
f([$hashref1, $hashref2]);
...
# and at some other point
f([\%hash]);
...

##</code><code>##

sub g {
    my ($arrayref_containing_just_one_hashref) = @_;
    my $hashref = $arrayref_containing_just_one_hashref->[0];
    # do something with $hashref
}