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Perl function prototype

I am trying to create a mypush routine with similar functionality to the built-in push function, but the code below is not working correctly.

    @planets = ('mercury', 'venus', 'earth', 'mars');
    myPush(@planets,"Test");

    sub myPush (\@@) {
         my $ref = shift;
         my @bal = @_;
         print "\@bal :  @bal\nRef : @{$ref}\n";
         #...
    }
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2 answers


In this line:

    myPush(@planets,"Test");

Perl hasn't seen a prototype yet, so it can't apply it. (If you turn on warnings, which you always should, you will get a message that main::myPush() called too early to check prototype

.)

You can either create your subroutine before using it:



    sub myPush (\@@) {
         my $ref = shift;
         my @bal = @_;
         print "\@bal :  @bal\nRef : @{$ref}\n";
         #...
    }

    @planets = ('mercury', 'venus', 'earth', 'mars');
    myPush(@planets,"Test");

or at least pre-declare it as your prototype:

    sub myPush (\@@);

    @planets = ('mercury', 'venus', 'earth', 'mars');
    myPush(@planets,"Test");

    sub myPush (\@@) {
         my $ref = shift;
         my @bal = @_;
         print "\@bal :  @bal\nRef : @{$ref}\n";
         #...
    }
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If you are sure about the functions and their names, you can simply put an ampersand in front of the call:



@planets = ('mercury', 'venus', 'earth', 'mars');
&myPush(@planets,"Test");

sub myPush (\@@) {
     my $ref = shift;
     my @bal = @_;
     print "\@bal :  @bal\nRef : @{$ref}\n";
     #...
}
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