I guess at this point, i am after some ideas as to how i could trigger an event only when both entry widgets have text in them. This event would change the state of the button.

Here is a way, polling

#!/usr/bin/perl --
use strict;
use warnings;
use Tk;
my $mw = tkinit;
my $bu = $mw -> Button(-text => "OK", -state=>'disabled')->pack();
my @te ;
push @te, $mw->Entry()->pack;
push @te, $mw->Entry()->pack;
$mw->repeat(
    900,
    sub {
        my $state = $bu->cget('-state') ;
        my $both = @te == grep { $_->index('end') } @te;
        if( $state ne 'normal' and $both ){
            $bu->configure( -state => 'normal' );
        } elsif( not $both ){
            $bu->configure( -state => 'disabled' );
        }
    },
);
MainLoop;
[download]

About every second, it checks to see if both Entry widgets have a text length greater than zero, and disables/enables the button