Yes, you're right, the OP did not specify this possibility, so this may or may not be needed. But taking this possibility into account was what made the solutions suggested by other monks slightly more complicated.

Note that you probably don't need to test $flag in the statements where you change its value. For example the loop of your first solution could be simplified as follows:

for (@$aref) {
    $flag = 1 if $_== 6;
    push @new, $_ unless $flag;
    $flag = 0 if $_== 7;    
}
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