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Re^3: Changing local variables in subroutine by passing by reference?

by ikegami (Patriarch)
on Feb 29, 2008 at 11:12 UTC ( [id://671147]=note: print w/replies, xml ) Need Help??


in reply to Re^2: Changing local variables in subroutine by passing by reference?
in thread Changing local variables in subroutine by passing by reference?

I don't think I understand the difference between "# another way, since @_ is an alias:"

In Perl, everything is passed by reference. To avoid confusion with Perl references — an unrelated concept — this is known as "aliasing" in the Perl world.

When a function is called, the elements of @_ are aliased to the arguments in the caller. Changes to @_ will be reflected in the arguments passed to the function.

In the following snippet, $_[0] is aliased to $x, and $_[1] is aliased to $y. Notice how changing @_ changed $x and $y, and notice how no references — and no dereferencing — were used.

sub func { print("f-pre: $_[0], $_[1]\n"); $_[0] = 5; $_[1] = 6; print("f-post: $_[0], $_[1]\n"); } my $x = 3; my $y = 4; print("pre: $x, $y\n"); func($x, $y); print("post: $x, $y\n");
pre: 3, 4 f-pre: 3, 4 f-post: 5, 6 post: 5, 6

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