G'day cr8josh,

It's unclear what you want because you haven't shown that.

Piecing together what's in your OP and "Re^2: Sort::Key::Natural sorting discrepancy", it seems you want a case-insensitive sort with underscores sorting before letters. In ASCII, uppercase letters (65-90) come before an underscore (95) which comes before lowercase letters (97-122). If that is indeed what you want, you can do it like this:

$ perl -E '
    my @x = (
        [qw{P007b_Yum P007_Yum}],
        [qw{P007B_YUM P007_YUM}],
        [qw{P007b_yum P007_yum}]
    ); 
    for (@x) { 
        say $_->[0] for sort { $a->[1] cmp $b->[1] } 
        map { [ $_, lc $_ ] } @$_; 
        say "-" x 3; 
    }
'
P007_Yum
P007b_Yum
---
P007_YUM
P007B_YUM
---
P007_yum
P007b_yum
---
[download]