Instead of the GRT, you can use the module Sort::Key::Multi that is faster, much easier to use and supports locale-aware sorting:

use Sort::Key::Multi qw(is_keysort il_keysort);
       # 'is_' and 'il_' indicate the sorting key types,
       # in that case:
       #   is = integer + string
       #   il = integer + locale_string

my @sorted = is_keysort { (/(.)(.*)/)[1,0] } @data;
my @locale_sorted = il_keysort { (/(.)(.*)/)[1,0] } @data;
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