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4.6 The foreach StatementYet another iteration construct is the foreach The original value of the scalar variable is automatically restored when the loop exits; another way to say this is that the scalar variable is local to the loop. Here's an example of a @a = (1,2,3,4,5); foreach $b (reverse @a) { print $b; } This program snippet prints You can omit the name of the scalar variable, in which case Perl pretends you have specified the
@a = (1,2,3,4,5); foreach (reverse @a) { print; } See how using the implied If the list you are iterating over is made of real variables rather than some function returning a list value, then the variable being used for iteration is in fact an alias for each variable in the list instead of being merely a copy of the values. Consequently, if you change the scalar variable, you are also changing that particular element in the list that the variable is standing in for. For example: @a = (3,5,7,9); foreach $one (@a) { $one *= 3; $x = 17; @a = (3,5,7,9); @b = (10,20,30); foreach $one (@a, @b, $x) { $one *= 3; } # $x is now 51 # @a is now (9,15,21,27) # @b is now (30,60,90); } # @a is now (9,15,21,27) Notice how altering |