You should investigate Tie::File bro'!

Here (stripped of all the HTML stuff) is an example of what you can do. To store your password entries you would do something like this:

#!/usr/bin/perl -w
use Tie::File;
use strict;
 
 
my @pwfile;
 
tie  @pwfile, 'Tie::File', 'pwfile.dat' or die $!;
 
my $user = {
            name => 'Klem Kaddiddlehopper',
            uid => 'kkhopper',
            addr => '123 main street, anywhere, anystate, 12345, USA',
            passwd => 'shhh!'
};
my @fields=qw / name uid addr passwd /;
#
# Add the record!
push @pwfile,join('|',map{ $user->{$_}} @fields );
[download]

and to read the entries you could do the following:

#!/usr/bin/perl -w
use Tie::File;
use strict;
 
 
my @pwfile;
 
tie  @pwfile, 'Tie::File', 'pwfile.dat' or die $!;
 
#
# Find a record
 
my $uid='kkhopper';
my $found=0;
foreach my $entry (@pwfile) {
  my @entries=split(/[\|]/,$entry);
  $found = 1 if ( $uid eq $entries[1]) and ($entries[3] eq 'shhh!' );
}
 
 
printf "WHHHOOOPPIE!\n" if $found;
[download]

I over simplified this for clarity sake.

I leave implementing this as part of your CGI up to your imagination.