sub pushSection {
    my ( $hashref, @secNames ) = @_;
    my $base = (sort @secNames)[0];
    $baselen = length $base;
    my $newBgn = "AA";
    my $grex = join( '|', @secNames );
    @pushees = sort grep( /^($grex)/, keys %$hashref );
    foreach $i (0 .. $#pushees) {
        $_ = $pushees[$i];
        my $txt = $hashref->{$_};
        delete $hashref->{$_};
        s/^($grex)(.*)/$base$newBgn$2/;
        $hashref->{$_} = $txt;
        $newBgn++ if ( $i < @pushees && length($pushees[$i+1]) == $baselen );
    }
}

chomp( @sections = <DATA> );
foreach (@sections) {
    next unless (/\S/); # not sure why I needed this
    $outline{$_} = "some text for section $_";
}
print "\nbefore:\n";
map {print "$_\t$outline{$_}\n"} sort keys %outline;

pushSection( \%outline, "AAAB", "AAAC" );

print "\nafter:\n";
map {print "$_\t$outline{$_}\n"} sort keys %outline;

__DATA__
AA
AAAA
AAAAAA
AAAB
AAAC
AAACAA
AAAD
AAAE

##</code><code>##

#before :: after
AA      :: AA
AAAA    :: AAAA
AAAAAA  :: AAAAAA
AAAB    :: AAABAA  # need to insert "AAAB" above this line
AAAC    :: AAABAB
AAACAA  :: AAABABAA
AAAD    :: AAAD    # need to rename this to "AAAC"
AAAE    :: AAAE    # need to rename this to "AAAD"