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 ];
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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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That way is to use pack to convert the numeric fields into binary values that will sort correctly using a string comparison function. It is convenient that binary encode integers (NOTE:In 'network' format only. That is 'N'&'n' *NOT* 'V'&'v') will sort correctly using a string comparison function.

Are you saying that although I always use locale; to ensure a prog behaves correctly in the local locale (eg sorting), there's something special about GRT that means I have to turn it off?

Incidentally, his results are sorted by num, then letter.

Chris

According to your locale, a byte with value 97 should be sorted before a byte with value 66.
That's fine if you're sorting iso-latin-1 text. It means "a" will be sorted earlier than "B".
That's not fine if you're sorting numbers in their native format.

@a = map unpack('N', $_),
     sort
     map pack('N', $_),
     65, 66, 67, 97, 98, 99;

  => 97, 65, 98, 66, 99, 67  using "use locale" on your system.
     a   A   b   B   c   C

  => 65, 66, 67, 97, 98, 99  using "no locale".
     A   B   C   a   b   c
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So yeah, you'd have to turn it off when it's comparing bytes representing numbers. But since you want it on for when it's comparing bytes representing text, you have a problem.

substr( $_, 1 ), substr( $_, 0, 1 ), $_ } on A437 should give
437 A A437
ie the nums are at the front regardless. The top code just shows that lower/uppercase is mixed or upper then lower, but nums are always first...

Sorry if it seems I'm being obtuse; I REALLY want to understand this.

Chris

You don't pass '437 A A437', you pass the result of pack('N A1 A*', '437', 'A', 'A437').

use Data::Dumper qw( Dumper );

for (qw[ A066 A067 A098 A099 ]) {
   my $coded = pack('N A1 A*', substr($_, 1), substr($_, 0, 1),  $_);
   local $Data::Dumper::Useqq = 1;
   local $Data::Dumper::Terse = 1;
   print("$_: ", Dumper($coded));
}
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A066: "\0\0\0BAA066"
A067: "\0\0\0CAA067"
A098: "\0\0\0bAA098"
A099: "\0\0\0cAA099"
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PS - Why do you keep replying to your node?