http://www.perlmonks.org?node_id=575923


in reply to shift vs @_

Well, if you mean why not use things from @_ directly: items in @_ are aliases to the things passed in; if you're not careful you can unintentionally modify something of your caller's.

my $foo = "bar"; sub bad_example { $_[0] =~ s/a/oo/; $_[0] } print "\$foo: $foo\n"; print "bad_example returns: ", bad_example( $foo ), "\n"; print "uh oh, \$foo: $foo\n";

Now if you just mean why not always use the my( $a, $b, $c ) = @_; form vice shift: there's times when you want to pull off some items and then do something list-y with the remaining contents of @_. Best example off the top of my head would be something that builds a hash from key/value pairs like:

sub take_one_and_hash { my $one = shift; my %hash = @_; ## frobulate $one based on %hash . . . }

Unless you pull that first argument off with shift you'd have to do something like @_[1..$#_] which just looks crufty.

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Re^2: shift vs @_
by jasonk (Parson) on Oct 02, 2006 at 19:41 UTC

    Now if you just mean why not always use the my( $a, $b, $c ) = @_; form vice shift: there's times when you want to pull off some items and then do something list-y with the remaining contents of @_. Best example off the top of my head would be something that builds a hash from key/value pairs like:

    Another good example is subclassing...

    sub do_something { my $self = shift; $self->SUPER::do_something( @_ ); # do some more stuff }

    We're not surrounded, we're in a target-rich environment!
Re^2: shift vs @_
by ambrus (Abbot) on Oct 07, 2006 at 11:52 UTC

    I don't usually use shift even if I want to do something with the rest of the arguments. I do, like, my($one, %hash) = @_;.