If you don't have some un-stated reason for using a hash (narrative, paras 1 and 2), and can take an array (narrative, para3), you need merely concatenate the $certName and  $validTo vars into a single, third var that you then push to your array -- as a pair, perhaps separated by a space. Here are three slightly variant approaches:

#!/usr/bin/perl
use 5.016;

my $certName = 'Hans';
my $validTo = '20130710';
my $thirdvar .= $certName;
$thirdvar .= ' ';
$thirdvar .= $validTo;
say "\$thirdvar: $thirdvar \n";

my $fourthvar = "$certName, $validTo";
say "\$fourthvar: $fourthvar \n";


my $fifthvar = $certName . " " . $validTo; 
say "\$fifthvar: $fifthvar";

=head

$thirdvar: Hans 20130710

$fourthvar: Hans, 20130710

$fifthvar: Hans 20130710

=cut
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