This may point you in a useful direction:

use strict;
use warnings;

my %param =
  (
  fname1 => "Fred", lname1 => 'Bloggs', email1 => 'fred@xyzzy.com',
  fname2 => "Joe", lname2 => 'Bloggs', email2 => 'joe@plugh.com',
  fname3 => "Sue", lname3 => 'Brown', phone3 => '555-1234-567',
  fname4 => "", lname4 => 'Brown', phone4 => '555-1234-567',
  fname5 => "Liz", lname4 => 'Green',
  );
my @entries; 

for my $key (keys %param)
  {
  my ($field, $num) = $key =~ /^(.*?)(\d+)/;
  next if ! defined $num;
  ${$entries[--$num]}{$field} = $param{$key} || '';
  }

for my $entry (@entries)
  {
  next unless ($$entry{lname} && $$entry{fname}); # Must have a full n
+ame
  next unless ($$entry{phone} || $$entry{email}); # Must have phone or
+ email
  $$entry{phone} ||= '';
  $$entry{email} ||= '';
  print "$$entry{lname},$$entry{fname},$$entry{phone},$$entry{email}\n
+";
  }
[download]

Prints:

Bloggs,Fred,,fred@xyzzy.com
Bloggs,Joe,,joe@plugh.com
Brown,Sue,555-1234-567,
[download]

Update to get closer to OP's requested behaviour

Now show us a code snippet with a populated version of param and a print that generates the sort of data you want to push into the DB. Something like:

use strict;
use warnings;

my %param =
  (
  fname1 => "Fred", lname1 => 'Bloggs', email1 => 'fred@xyzzy.com',
  fname2 => "Joe", lname2 => 'Bloggs', email2 => 'joe@plugh.com',
  fname3 => "Sue", lname3 => 'Brown', phone1 => '555-1234-567',
  );
my @entries; 

#generate entries from parameters

print join "\n", @entries;
__END__
[download]

Prints:

Bloggs,Fred,,fred@xyzzy.com
Bloggs,Joe,,joe@plugh.com
Brown,Sue,555-1234-567,
[download]

Hi.

Using your data structure, this is what I aim to do.

my %param =
  (
  fname1 => "Fred", lname1 => 'Bloggs', email1 => 'fred@xyzzy.com',
  fname2 => "Joe", lname2 => 'Bloggs', email2 => 'joe@plugh.com',
  fname3 => "Sue", lname3 => 'Brown', phone1 => '555-1234-567',
  );


# assuming everything above passes the sanity check
my $stored = qq(INSERT INTO addbook (fname, lname, phone, address, ema
+il) VALUES(?,?,?,?,?);
my $sth = $dbh->prepare($data);
$sth->execute($fname#, $lname#, $phone#, $address#, $email#) or die $d
+bh->errstr;
[download]

Each row of fields has to be entered into my database like that.

Thank you. </code>

Thanks for your help.