I know you asked for a RegEx , and @rray posted the solution that does exactly what you requested (and that has already taken my +1). Anyway I find it important to comment that PHP already has a solution made as a glove for your specific case, and does not need RegEx .
Just this, clean and short of writing:
'ALL'.strstr( '99-01[10-10-2010]', '-' );
An example code:
$s = '99-01[10-10-2010]';
echo 'ALL'.strstr( $s, '-' );
Iterating an array :
$strings = array(
foreach( $strings as $s ) echo 'ALL'.strstr( $s, '-' );
See working at IDEONE .