I wrote this but it is only working if the variables are set with "our".

That works with my variables as well. However, those variables have to be in the same scope as your display_init function:

my $i = 42;
my $j = 'FreeBSD';

sub display_init {
        my @variables = @_;
        my $value;

        foreach (@variables) {
                eval("\$value=\$$_");
                if (! defined($value) ) { $value = "undefined"; }
                print "$_ : $value\n";
        }
}
display_init (qw( i j));
__END__
i : 42
j : FreeBSD
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_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

eval EXPR is capable of accessing lexicals.

my $t = 'test';
print eval '$t';  # test
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As long as it can "see" them (i.e. As long as they are in scope)

my $t1 = 'test1';
sub show { print eval "\$$_" for @_; }
my $t2 = 'test2';
show(qw( t1 t2 ));  # test1, but not test2
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It can't see a variable that no longer exists.

{
   my $t = 'test';
   sub show { print eval "\$$_" for @_; }
}
show(qw( t ));  # Nothing
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It can't see a variable that is no longer in scope.

{
   my $t = 'test';
   sub foo { $t }
   sub show { print eval "\$$_" for @_; }
}
show(qw( t ));  # Nothing
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...unless the function with the eval EXPR captured it.

{
   my $t = 'test';
   sub show { $t; print eval "\$$_" for @_; }
}
show(qw( t ));  # test
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Anyway, why aren't you passing the variable's value instead of its name?

Also see Coping With Scoping

Thanks for all your answers, but it seems i am missing something.
if i write


my $t;
sub show { print eval "\$$_" for @_; }
sub init { $t = 'test'; show(qw( t )); }

=> nothing
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but if i write


my $t;
sub show { print $t; print eval "\$$_" for @_; }
sub init { $t = 'test'; show(qw( t )); }

=> testtest
[download]

So it seems eval can not find $t in the right scope but if i use $t in a usual way before calling eval, it can find it...

Fact of the matter is that I never use it. Inserting normal print/warn/die statements just comes more natural after all this time. The code is essentially the first version that ran, I never bothered to clean it up. Anyway, here it is:

You could look at PadWalker to get access to lexical variables.

Clint

Update Thanks to ikegami for pointing out that you are not using symbolic references. I misread the code.

Presumably then, your my variables are being declared within other subs, so they are not in the same scope as your display_init sub, and so are not visible.

He's not using sym refs.