use feature qw( say refaliasing );
no warnings qw( experimental::refaliasing );

my @stack;

sub padsv { \$stack[@stack] = \$_[0]; }

sub const { \$stack[@stack] = \$_[0]; }

sub add_equal {
   \my $rhs = \pop(@stack);
   \my $lhs = \pop(@stack);
   \my $rv = \( $lhs += $rhs );
   \$stack[@stack] = \$rv
}

sub add {
   \my $rhs = \pop(@stack);
   \my $lhs = \pop(@stack);
   \my $rv = \( $lhs + $rhs );
   \$stack[@stack] = \$rv
}

sub minus {
   \my $rhs = \pop(@stack);
   \my $lhs = \pop(@stack);
   \my $rv = \( $lhs - $rhs );
   \$stack[@stack] = \$rv
}

sub range {
   \my $rhs = \pop(@stack);
   \my $lhs = \pop(@stack);
#say "$lhs..$rhs";
   \$stack[@stack] = \$_ for $lhs .. $rhs;
}

my $i = 4;               # $i  @stack
                         # --  -------
padsv($i);               #  4  $i
padsv($i);               #  4  $i,$i
const(3);                #  4  $i,$i,3
add_equal();             #  7  $i,7
const(1);                #  7  $i,7,1
minus();                 #  7  $i,6
range();                 #  7  -

say join ', ', @stack;   # ""

##</code><code>##

my $i = 4;               # $i  @stack
                         # --  -------
padsv($i);               #  4  $i
const(0);                #  4  $i,0
add();                   #  4  4
padsv($i);               #  4  4,$i
const(3);                #  4  4,$i,3
plus_equal();            #  7  4,7
const(1);                #  7  4,7,1
minus();                 #  7  4,6
range();                 #  7  4,5,6

say join ', ', @stack;   # "4, 5, 6"