printf( "\n$_: " ), 
m[A( [^Z]*|)Z] and print "'$1'" 
    for 'AZ', 'A SOMETHING Z', 'ASOMETHINGZ', 'A Z', 'A  Z';;

AZ: ''

A SOMETHING Z: ' SOMETHING '

ASOMETHINGZ:
A Z: ' '

A  Z: '  '