printf "next is %s\n", next_file($_)
    for qw( a.png dpq.jpg zx.png ott.jpg zzz.tiff oi.png );

##</code><code>##

sub next_file {
    ...
    my @alphabet = qw/a b c d e f g h j k m n p q r s t u v w x y z/;

##</code><code>##

{
    my @alphabet;

    BEGIN { @alphabet = ('a' .. 'h', 'j', 'k', 'm', 'n', 'p' .. 'z'); }

    sub next_file
    {
        ...
    }
}

##</code><code>##

$previous =~ /(.*)\.(.*)/;
my $word = $1;
my $ext  = $2;

##</code><code>##

my ($word, $ext) = $previous =~ /(.*)\.(.*)/;