It's all a matter of what's being passed in, and how the function accepts it. You can pass anything you want into a function, so you need to be sure that you're passing what the function wants.

Here's two samples:

my @files = qw( foo bar bat );
@files = byvalue( @files );
byreference( \@files );


sub add_txt_by_value {
    my @array = @_;

    foreach ( @array ) {
        $_ .= ".txt";
    }
    return @array;
}

sub add_txt_by_reference {
    my $arrayref = shift;
    
    foreach ( @$arrayref ) {
       $_ .= ".txt";
    }
}
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Note that when we pass by value, we have to pass back the array as a return value. When we pass by ref, we're modifying the array in the caller's space.

Updated: s/$array/$arrayref/ in the second example. Thanks, Hofmator.

xoxo,
Andy
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