my $shorter = min( $lenString1, $lenString2 );
my $longer  = max( $lenString1, $lenString2 );

## longer to shorter
my $et = 'DI' x $shorter . 'D' x ( $longer - $shorter );

## or shorter to longer
my $et = 'DI' x $shorter . 'I' x ( $longer - $shorter );

##</code><code>##

## longer to shorter
my $et = 'D' x $longer . 'I' x $shorter;

## shorter to longer
my $et = 'D' x $shorter . 'I' x $longer;

##</code><code>##

'the quick brown fox'
'before the quick brown fox'