Re: 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";
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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 $one based on %hash . . .
}
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Unless you pull that first argument off with shift you'd have to do something like @_[1..$#_] 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
}
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We're not surrounded, we're in a target-rich environment!

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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) = @_;.

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