Yes, but turning a single use of a lexical variable into a warning will raise warnings for code like:

use Guard;
sub foo {
    $guard = scope_guard { print "done\n" };
    ... do stuff, without ever mentioning $guard again ...
};
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This could maybe circumvented by only raising the warning when my is missing:

use Guard;
sub foo {
    # This will warn
    $guard = scope_guard { print "done\n" };
    ... do stuff, without ever mentioning $guard again ...
};
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Detecting this will be tricky, but it should catch most of the typos that would get a warning.