G'day starfire4444,

Welcome to the Monastery.

When you call a subroutine with a leading '&', you are specifying that you wish to ignore whatever prototype you used in the subroutine definition. Did you use a prototype? If so, do you want to ignore it?

In almost all cases, the answer to first question is NO: consequently, the second conditional question is not applicable. Unless you know exactly what you're doing, and are able to explain with unerring clarity why you're doing it, never call a subroutine with a leading ampersand.

At this point, it may be useful to read the SYNOPSIS of perlsub.

I strongly suspect that your definition of get_value2 does not include a prototype. If it does, you need to show it. If it doesn't, adding an ampersand makes no difference; however, its presence suggests that a prototype was involved: be wary of angry maintenance programmers with clenched fists; read about hubris in perlglossary.

Now, let's just take this one step at a time:

  1. Printing the return value directly: 

    $ perl -wE 'sub f { 42 } say f()'
42
$ perl -wE 'sub f { 42 } say &f()'
42

    [download]

  2. Saving the return value and then printing: 

    $ perl -wE 'sub f { 42 } my $x = f(); say $x'
42
$ perl -wE 'sub f { 42 } my $x = &f(); say $x'
42

    [download]

  3. Saving a reference to the return value and then printing: 

    $ perl -wE 'sub f { 42 } my $x = \f(); say $x'
SCALAR(0x7fc8f2805480)
$ perl -wE 'sub f { 42 } my $x = \&f(); say $x'
SCALAR(0x7f9783805480)

    [download]

  4. Saving a reference to the return value and then printing the dereferenced return value: 

    $ perl -wE 'sub f { 42 } my $x = \f(); say $$x'
42
$ perl -wE 'sub f { 42 } my $x = \&f(); say $$x'
42

    [download]

As I hope you can now see, adding an ampersand when calling a subroutine, which was defined without a prototype, serves no purpose whatsoever other than to appease whomsoever personifies Confusion in whatever mythos you subscribe to.

[Aside: What you're referring to as the dot operator is, in fact, the string concatenation operator: see "perlop: Additive Operators".]

— Ken

In reply to Re: subroutine / dot operator / hash vlaue by kcott
in thread subroutine / dot operator / hash vlaue by starfire4444

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