#!/usr/bin/perl -wT

use strict;
use CGI;
use Image::Size;

my $q = new CGI;

my $imageDir = "./";
my @images;

opendir DIR, "$imageDir" or die "Can't open $imageDir $!";
    @images = grep { /\.(?:png|gif|jpg)$/i } readdir DIR;
closedir DIR;

print $q->header("text/html"),
      $q->start_html("Images in $imageDir"),
      $q->p("Here are all the images in $imageDir");

foreach my $image (@images) {
    my ($width, $height) = imgsize("$image");
    print $q->p(
            $q->a({-href=>$image},
              $q->img({-src=>$image,
                       -width=>$width,
                       -height=>$height})
            )
    );
}

print $q->end_html;
[download]

Update: Applied gav^'s and dws's suggestions listed below.

Update: Included jarich's code to use CGI.pm to print out the lines in the foreach loop.