It seems to me that regardless of locale/no locale, it should sort nums before letters, as per BrowserUK's tutorial.
What numbers? You don't provide any numbers to sort. You first convert the numbers into strings of 4 characters. The resulting characters could be anything, including letters. sort is doing a lexical sort on them as requested, and applies locale rules as requested even though it makes no sense to do so.
In this specific case, locale could very well affect how "µ" and "Ù" sort.
my $NUL = chr(0x00);
my $SOH = chr(0x01);
my $STX = chr(0x02);
my $undef93 = chr(0x93);
001: "${NUL}${NUL}${NUL}${SOH}"
123: "${NUL}${NUL}${NUL}{"
222: "${NUL}${NUL}${NUL}Þ"
437: "${NUL}${NUL}${SOH}µ"
473: "${NUL}${NUL}${SOH}Ù"
659: "${NUL}${NUL}${STX}${undef93}"
Since you want part of the string sorted numerically and part of the string sorted lexically (using the locale), you'll have to limit yourself to the ST.
@arr = map{ $_->[0] }
sort { $a->[1] <=> $b->[1] || $a->[2] cmp $b->[2] }
map{ [ $_, substr( $_, 1 ), substr( $_, 0, 1 ) ] }
qw[ A473 B437 B659 C659 C123 D123 D222 E222 E001 A001 ];
