If you use warnings in your Perl code you might encounter this strange warning. It is especially strange as the code seems to be working as expected. Nevertheless this is one of the common warnings in Perl. You'd better understand it and get rid of it. Without disabling warnings.

Access element of an array

In this most simple example we have an array called @names and we try to print the first element in the array by accessing @names[0];.

examples/array_index1.pl



use warnings; use strict; use 5.010; my @names = qw(Foo Bar); say @names[0];

The output looks like this:

Scalar value @names[0] better written as $names[0] at array_index1.pl line 6. Foo

So we get the correct value printed, but we also get a warning.

In Perl, when you talk about a whole array or about a slice of an array you use the @ sigil, but when you try to access a single element of an array you need to use the $ sigil. So the proper way to access the first element of the @names array is to use $names[0].

Array element in dereference

In the second example we have slightly more complex expression,

examples/array_index2.pl



use warnings; use strict; sub f { my @prevCommands = @{ @_[0] }; }

Running this code we only get the warning but no output. The function does not even get executed, the warning is already emitted.

Scalar value @_[0] better written as $_[0] at array_index2.pl line 5.

Here too, instead of @_[0] we should have written $_[0]. Not to be confused with $_ the default variable of Perl that does not have a square-bracket nor curly braces after it.

Correct way to access elements of an array in Perl

The correct way can be seen in this code:

examples/array_index.pl



use warnings; use strict; use 5.010; my @names = qw(Foo Bar); say $names[0]; sub f { my @prevCommands = @{ $_[0] }; }