{ my \$x = 1; my \$y = 4; # The initial values are saved. my @a; foreach (\$x..\$y) { push @a, \$_; \$y++; } print("@a\n"); # 1 2 3 4 } { my \$x = 1; my \$y = 4; # The initial values are saved. my @a; foreach (reverse \$x..\$y) { push @a, \$_; \$x--; } print("@a\n"); # 4 3 2 1 } { my @a = (1, 2, 3, 4); my \$i = 5; # Loops "while (pass_num < @a)". # In this case, that means loop forever. foreach (@a) { # Loops "while (pass_num < @a)" push(@a, \$i++); if (@a == 20) { push(@a, '...'); last; } # Avoid infinite loop. } print("@a\n"); # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 ... } { my @a = (1, 2); my @b = (3, 4); my \$i = 5; # Creates a list at the start of the # loop and iterates over that list. # In this case, elements are added to @b, # but not to the list on the stack, so # it loops 4 times. foreach (@a, @b) { push(@b, \$i++); } print("@a @b\n"); # 1 2 3 4 5 6 7 8 } ##```## >perl -le "for (1..2) { for (reverse 1..3) { print; \$_=5; } }" 3 2 1 5 5 5 >perl -le "for (1..2) { for (reverse 1..(\$x=3)) { print; \$_=5; } }" 3 2 1 3 2 1 ```