This demonstrates the basic technique for your needs. You will need to read up on perlfunc:open to find out how to open your files rather than using embedded (inline) files as I am here. You'll also need to look in perlrun and perlop if you want to supply the filenames on the command line rather than hard coding them.

Hope this helps. If you have problems with converting the code to your needs, post your attempt and any errors and we'll try and help you further.

#! perl -sw
use strict;
use Inline::Files;

my %second = map{ /^(\d+),.*$/; $1 => undef }<SECOND>;

while(<FIRST>) {
    /^(\d+),.*$/;
    print if not exists $second{$1};
}
 exit;
__FIRST__
1524781,Anderson,Jon,srv01,jon,12-05-02.
1843552,Bruford,William,srv01,william,12-17-02.
7589243,Howe,Steven,srv01,steven,12-05-02.
0547629,Squire,Chris,srv01,chris,12-05-02.
5486135,Wakeman,Rick,srv01,rick,12-17-02.
__SECOND__
1524781,Anderson,Jon,srv01,jon,12-05-02.
1843552,Bruford,William,srv01,william,12-17-02.
0547629,Squire,Chris,srv01,chris,12-05-02.
[download]

Gives this output.

C:\test>215414
7589243,Howe,Steven,srv01,steven,12-05-02.
5486135,Wakeman,Rick,srv01,rick,12-17-02.

C:\test>
[download]