CODEWITHSUNDEEP
perlvariableshashevalconfig
Travv92
Travv92

Reputation: 801

Setting variables in perl config file eval

I've got a perl script and a .config file and want to store some hashes in the config file with some variables as its value, then dynamically change them from my perl script.

Config File:

$hash{"hello"} = ["$blah", "$blah2"];

And my perl script:

if (-e ".config")
{
    $blah = "hello";
    $blah2 = "world!";

    eval ('require(".config")');

    $val1 = $hash{"hello"}[0];
    $val2 = $hash{"hello"}[1];
    print "$val1 $val2\n";

    # Now I want to CHANGE blah and blah2
    $blah = "world!";
    $blah2 = "hello";

    $val1 = $hash{"hello"}[0];
    $val2 = $hash{"hello"}[1];
    print "$val1 $val2\n";
}

But both prints show hello world! as if the change didn't happen.. Am I missing something?

Thanks.

Upvotes: 0

Views: 1119

Answers (1)

Dave Sherohman
Dave Sherohman

Reputation: 46245

(Strange... I've never seen a question of this sort previously, and then variations on it (which are different enough to clearly not be just a cross-post) appeared both here and on PerlMonks in the same day.)

The point you're missing is that

$hash{"hello"} = ["$blah", "$blah2"];

just copies the values of $blah and $blah2 into (an anonymous array referenced by) $hash{hello}. It does not create any lasting connection between the hash and $blah/$blah2.

As a side note, none of the quotes in that line serve any purpose. It would more commonly be written as:

$hash{hello} = [$blah, $blah2];

Or, if you want to create references so that $blah and $hash{hello}[0] are forever linked and changing one will also change the other:

$hash{hello} = [\$blah, \$blah2];

Note that in this case, you must not use quotes. Although "$blah" and $blah are equivalent, "\$blah" and \$blah are not - \$blah gives you a reference to $blah, but "\$blah" gives you the literal string "$blah" with no variables involved at all.

Upvotes: 2

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