Something like this?

#!/usr/bin/perl
use warnings;
use strict;

while (<DATA>) {
    chomp;
    my @names = map lc, split;
    s/\.// for @names;
    print join "\t",
        $_,
        lc substr($names[0], 0, 1) . $names[-1],
        lc join '.', @names;
    print "\n"
}

__DATA__
Max Maier
Jerome Mustermann
John Lee Duke
Peter F. Smith
[download]

Your treatment of the middle names might be different. Also, if there are non-ASCII characters in your users' names, more care is needed. Moreover, you should probably hash the usernames and e-mails and check for duplicates.