use strict 'vars'; let's the programmer know that a variable they used doesn't exist.
Could you first define what you mean by exists in this context? Because: 
package main;
use strict 'vars';
say $var;    # Error, ($var doesn't "exist"?)

[download]
package main;
use strict 'vars';
say $::var;  # No error ($::var does "exist"?)

[download]
But that's clearly nonsense as in both snippets, $var and $::var are the same, and a variable cannot both exist and not exist.

In reply to Re^13: Using a sting with a variable name by JavaFan
in thread Using a sting with a variable name by bingohighway

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