./qr_test.pl 'atuvwxz' 'qr/ ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) (w) (x) ) ( z ) /x'
+ ./qr_test.pl atuvwxz 'qr/ ( a )  (?| x ( y ) z () () ()| (p (q) r) | (t) u (v) (w) (x) ) ( z ) /x'
qr=(?x-ism: ( a )  (?| x ( y ) z () () ()| (p (q) r) | (t) u (v) (w) (x) ) ( z ) )
string=atuvwxz
(?x-ism: ( a )  (?| x ( y ) z () () ()| (p (q) r) | (t) u (v) (w) (x) ) ( z ) ) present
1=a
2=t
3=v
4=w
5=x
6=z