You could use symbolic references, but don't do that. I'd probably use a hash array instead of constant if I were going to store this sort of stuff in a config file.

An alternative is to use the string as a method to the package where the constants are defined, e.g.:

package Foo;

use constant LOG_DEBUG => 0;

package main;

my $log_level = 'LOG_DEBUG';

print Foo->$log_level, "\n";
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