First, you need to know that neither of these has anything *directly* to do with references. I recommend the documentation on shift to you; one thing to keep in mind here is that, inside a subroutine, the *default argument* to shift is @_ (outside, it's @ARGV which holds the arguments passed to the script), so that shift is really shift @_.

The first line you give returns the first member of @_, making @_ one element shorter (as per the documentation for shift); the second will set $myarray to the *number* of entries in the @_ array (because you're evaluating it in a scalar context).

The first is appropriate if you want to get a single argument from @_. The second is useful if you know you need a certain number of arguments, and want to print an error message if there aren't enough. An importantly different syntax is my ($myarray) = @_; (note parens), which evaluates @_ in *list context* and will return the first element of @_ (without removing it from @_, like shift does).

(if you got the impression that this context business is rather important stuff, you got the right impression =)

HTH!

perl -e 'print "How sweet does a rose smell? "; chomp ($n = <STDIN>); 
+$rose = "smells sweet to degree $n"; *other_name = *rose; print "$oth
+er_name\n"'
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