Accessing Elements of an Array

If you've used arrays in another programming language, you won't be surprised to find that Perl provides a way to subscript an array in order to refer to an element by a numeric index.

The array elements are numbered using sequential integers, beginning at zero and increasing by one for each element, like this:

	$fred[0] = 'yabba";
	$fred[1] = 'dabba";
	$fred[2] = 'doo";

The array name itself (in this case, @fred) is from a completely separate namespace than scalars use; you could have a scalar variable named $fred in the same program, and Perl will treat them as different things, and wouldn't be confused.¹   (Your maintenance programmer might be confused, though, so don't capriciously make all of your variable names the same!)

You can use an array element like $fred[2] in almost every place ² where you could use any other scalar variable like $fred.  For example, you can get the value from an array element or change that value by the same sorts of expressions we used in the sessions on scalar variables:

	print $fred[0];
	$fred[2] = "diddley";
	$fred[1] .= "whatsis";

Of course, the subscript may be any expression that gives a numeric value.  If it's not an integer already, it'll automatically be truncated to the next lower integer:

	$number = 2.71828;
	print $fred[$number - 1];	# Same as printing $fred[1]

If the subscript indicates an element that would be beyond the end of the array, the corresponding value will be undef.  This is just as with ordinary scalars; if your program has never stored a value into a scalar variable, then it's initial value is undef.

	$blank = $fred[ 142_857 ];	# unused array element gives undef
	$blanc = $mel;			# unused scalar $mel also gives undef

[1] The syntax is always unambiguous - tricky perhaps, but unambiguous.

Return to the page from whence you came

[2] The most notable excepton is that the control variable of a foreach loop, which we'll see in a later lesson, must be a simple scalar.  And there are others, like the "indirect object slot" and "indirect filehandle slot" for print and printf.

Return to the page from whence you came