What is the difference between Perl subroutines with "&" (ampersand) and without

Question

What is the difference between the next two lines in Perl:

PopupMsg("Hello");

&PopupMsg("Hello");

...

sub PopupMsg
{
    subroutines code here...
}

please notice that in some cases I must use the first line and in some the second, other wise I get an error.

Please give an example of when you have to use the second form. — Borodin, Mar 12 '14 at 14:06
[Perl using the special character &](http://stackoverflow.com/questions/17173783/perl-using-the-special-character/17173958#17173958) — Miller, Mar 12 '14 at 18:40

score 5 · Answer 1 · edited Mar 12 '14 at 15:41

5

It is bad practice to call subroutines using the ampersand &. As long as you use parentheses or have predeclared the symbol as a subroutine name, the call will compile fine.

The ampersand is necessary when you are dealing with the subroutine as a data item, for instance to take a reference to it.

my $sub = \&PopupMsg;

edited Mar 12 '14 at 15:41

Dave Sherohman

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answered Mar 12 '14 at 14:05

Borodin

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score 3 · Answer 2 · answered Mar 12 '14 at 14:02

See http://perldoc.perl.org/perlsub.html:

NAME(LIST);  # & is optional with parentheses.
NAME LIST;   # Parentheses optional if predeclared/imported.
&NAME(LIST); # Circumvent prototypes.
&NAME;       # Makes current @_ visible to called subroutine.

Prototypes explained further down in http://perldoc.perl.org/perlsub.html#Prototypes.

What is the difference between Perl subroutines with "&" (ampersand) and without

2 Answers2