If you find a module you want to use, just

perl -e 'use <insert_Name_of_Module>'
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To scan the files in a particular directory, just use the builtins readdir and opendir. Then, to get their modification time use stat. If you need to recurse into subdirectories, you might need File::Find.

To create a webpage, just print you tags and data to a new HTML file. If you want to trigger the scan from a web page to a make a web application, then use CGI.

Most people use the DBI module to access databases.

File::Copy is an obvious choice for copying files.

Pretty much none. At least from CPAN, specifically. :) opendir and readdir (or File::Find if you need to look down a directory tree), Digest::MD5, CGI, and File::Copy are core modules which ship with Perl.

DBI and the appropriate DBD::Foo driver for your database would need to be installed from CPAN.

I want to scan all the files in a directory. Find the ones that have been modified since I last run the program.

opendir, readdir for reading a single directory, File::Find to read recursively. Calculate a checksum with e.g. Digest::MD5 and store filenames and checksum in a database, probably a self-contained like DBI::SQLite.

Present them on a web page.

Select a subset of them. Save the subset to a database.

Copy the subset to across to another directory.

File::Copy

TIMTOWDI - these are just the apples I can think of that hang lowest, and are easiest to pick.

--shmem

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

find2perl /mydir -type f -newer lasttime -print > find-recent-files.pl

gets you some perl that is close to what you want, and you can change the strings '/mydir' and 'lasttime' to command line input.

#! /opt/local/bin/perl -w
    eval 'exec /opt/local/bin/perl -S $0 ${1+"$@"}'
        if 0; #$running_under_some_shell

use strict;
use File::Find ();

use vars qw/*name *dir *prune/;
*name   = *File::Find::name;
*dir    = *File::Find::dir;
*prune  = *File::Find::prune;

sub wanted;

my $timefile = shift;
my $rootdir = shift;

(-e "$timefile") or die "$0 : last mod time file \"$timefile\" does no
+t exist\n";
(-d "$rootdir") or die "$0 : directory \"$rootdir\" for search does no
+t exist\n";

my $AGE_OFlasttime = -M "$timefile";


# Traverse desired filesystems
File::Find::find({wanted => \&wanted}, "$rootdir");
exit;

sub wanted {
    my ($dev,$ino,$mode,$nlink,$uid,$gid);

    (($dev,$ino,$mode,$nlink,$uid,$gid) = lstat($_)) &&
    -f _ &&
    (-M _ < $AGE_OFlasttime) &&
    print("$name\n");
}
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