I was looking at a article ... wanted make sure I was interpreting (pun intended) the mechanism correctly:

:) Consider interpreting the article instead , or one of these (: not sure if this was punny :)

:D

Schwartzian Transform

How do I sort an array by (anything)?

Schwartzian Transform

Schwartzian Transform

Efficient sorting using the Schwartzian Transform

site:perlmonks.org Schwartzian Transform

Guttman-Rosler Transforms

Renaming the Schwartzian Transform

Sorting dates with the Schwartzian Transform

dominus Schwartzian transform

Schwartzian transform

The Perl Hardware Store - Tools You Didn't Know You Needed

Sorting with the Schwartzian Transform (May 06)

Am I close to understanding it? Is the Schwartzian Transform *always* constructed in this manner?

Close, just need some Basic debugging checklist to cement your understanding

$ cd dominus-tmp

$ cat schwartz
#!/usr/bin/perl --
use strict;
use warnings;
use Data::Dump qw/ dd pp /;

my @sorted_names ;


opendir D, '.' or die $!;
@sorted_names =
    map { [ $_, -M $_ ] }
    readdir D;
dd \@sorted_names;

opendir D, '.' or die $!;
@sorted_names =
    sort { $b->[1] <=> $a->[1] }
    map { [ $_, -M $_ ] }
    readdir D;
dd \@sorted_names;

opendir D, '.' or die $!;
@sorted_names =
    map { $_->[0] }
    sort { $b->[1] <=> $a->[1] }
    map { [ $_, -M $_ ] }
    readdir D;
dd \@sorted_names;
__END__


$ perl schwartz
[
  [".", 0.00197916666666667],
  ["..", 0.00247685185185185],
  ["schwartz", 0.000289351851851852],
]
[
  ["..", 0.00247685185185185],
  [".", 0.00197916666666667],
  ["schwartz", 0.000289351851851852],
]
["..", ".", "schwartz"]
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The  [ $_, -M $_ ] } part is known as  [ $_, expensive_function( $_ ) ]