With sort and a regexp:

#!/usr/bin/perl -w
use strict;

my $re = qr/\| \w+ \s+ (\w+) \|/msx;

print sort { 
    my ($aa) = $a =~ $re;
    my ($bb) = $b =~ $re;
    $aa cmp $bb;
    } <DATA>;


__DATA__
123|Pete Smith|4321|321G4
2134|Mike Malarky|93F821
83|Dave Waylaid|8374W

Output :
2134|Mike Malarky|93F821
123|Pete Smith|4321|321G4
83|Dave Waylaid|8374W
[download]

hth,
PooLpi