The underscore (_) comes after the decimals and capital letters using perl's cmp operator but before the lower case letters. If you'd like it to be before numbers, then simply create a custom sort by moving it before:

use strict;
use warnings;

my @foods = qw(abc abc1 abc2 abc_1 abc_2 abc01_1);

# Create a Custom Sort
my @sort_char_order = sort map {chr $_} (1..127);
# Move '_' to before '0' in your list;
my @your_char_order = map {$_ eq '0' ? ('_', '0') : $_ eq '_' ? () : $
+_} @sort_char_order;
my $sort_char_order = join '', @sort_char_order;
my $your_char_order = join '', @your_char_order;

my $trans_word = eval qq{
    sub {
        my \$param = shift;
        \$param =~ tr/\Q$your_char_order\E/\Q$sort_char_order\E/;
        return \$param;
    }
};

# Sort by your custom definition
my @sorted_foods = 
    map { $_->[0] }
    sort { $a->[1] cmp $b->[1] }
    map { [ $_, $trans_word->($_) ] } @foods;
    
print join ' ', @sorted_foods;
# abc abc_1 abc_2 abc01_1 abc1 abc2
[download]

- Miller

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