johngg@shiraz:~ > perl -Mstrict -Mwarnings -E '
my @arr = ( 2, 6, 5, 7, 4, 3, 9 );
my @sub = shift @arr;
push @sub,
   $arr[ 0 ] > $sub[ -1 ]
   ? shift @arr
   : do { shift @arr; () }
   while @arr;
say for @sub;'
2
6
7
9