#!perl -l
print $_="the thing that that thing does";
/(\w+) that/    and printf '$&=%-20s $1=%-10s %s',$&,$1,$/;
/($1) (\w+)/    and printf '$&=%-20s $1=%-10s $2=%-10s %s',$&,$1,$2,$/;
/$1 (\w+) (\1)/ and printf '$&=%-20s $1=%-10s $2=%-10s %s',$&,$1,$2,$/;
__END__
the thing that that thing does
$&=thing that           $1=thing      
$&=thing that           $1=thing      $2=that       
$&=thing that that      $1=that       $2=that