The downside is that the eval markly reduces the efficiency.

So, just do one eval() . . .

sub ATOa {
    my $code = '('
             . join( ',', map { "\\substr(\$_[0], $_)" } 0 .. length( 
+$_[0] ) )
             . ')';
    return eval $code;
}
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-sauoq
"My two cents aren't worth a dime.";