variable with $$

[Anonymous Monk]

hello monks , I have a variable like that :

my $name = Sam;

what I wanna do is create a variable from reading $name which will look like this :

my $newvar = $Sam;

so I want to print the value for name with a $ in the front of it. I tried :

my $newvar = $\"$name";
or 
my $newvar = '$'"$name";

no luck ,, any idea? can someone help? thanks

[bart]

You're asking for symbolic references, huh? At least, I think you are. Well: don't do it, unless you know really well what you're doing — and basically, if you have to ask how to do it, I dare to bet that you don't. Making a name based on a user's input is always very dangerous. You never know whether he'll input the name of a variable you've used yourself in your program.

See dominus' classic 3 articles on his website, for more arguments against it:

1. Why it's stupid to `use a variable as a variable name'
2. A More Direct Explanation of the Problem
3. What if I'm Really Careful?

In general: don't do it. Use a hash. Like this:

my %v;   # my hash for user variables
$v{Sam}++; 
# or:
my $name = 'Sam';
$v{$name}++;

Oh, and if you really want to do it, try $$name or ${$name}, which both do the same thing, and only work on global (= package) variables — and only with no strict 'refs'. Just to show you it can be done... ;-)

If all you want is to work on predefined variables with no input from the user/outside world, try hard references instead.

my $var = \$sam;
$$var++;  # increments $sam

Yes, the syntax is exactly the same. That's one reason why coding without strict 'refs' in place, is a rather bad idea.

[The Mad Hatter]

Put $name in double quotes and then backslash (escape) the extra $...

my $name = "Sam";
my $newvar = "\$$name";
# or even ... my $newvar = '$' . $name;

print $name, "\n", $newvar;

which prints

Sam
$Sam

[kvale]

You can do this with

my $name = "Sam";
my $newvar = '$' . $name;

[Anonymous Monk]

thanks all

[zentara]

Yep, it is far from my lowly status to say that Bart is right, but he is. Whenever you start thinking about using a "variable in a variable" just stop!!...and think how can I do this with a hash? It will save you tons of trouble, and once you get the "hang of hashes", you'll love them.

[Steve_p]

Try...

my $newvar = "\$" . "$name";

[asarih]

$var="test";
$test="fred";
print ${$var};


update Note to self: read thoroughly before post.