: I have the following code to sort an array of dirs/files:
:
:     @sorted = sort { -M $b <=> -M $a } @logfile;
:     foreach $lastfilemod (@sorted) {
:         $dir = (dirname $lastfilemod);
:         if (! exists $srt{$dir} ) {
:             push(@srtlist, $lastfilemod);
:             $srt{$dir} = 1;
:         }
:     }
:
: The @logfile looks like:
:
: /dir/dir/file1
: /dir/dir/file2
: /dir/dir2/file1
: ...
:
: What I was trying to do is have @sorted list the files by last
: modified and then I could print out each file last modified in one per
: directory. However the sort isn't working correctly and I'm not
: getting the last file modified for some directories. Could anyone
: point out what I'm doing wrong?

For each file, remember it if it was modified more recently than the
current frontrunner for the file's parent directory:

    $ cat try
    #! /usr/bin/perl

    use warnings;
    use strict;

    use File::Basename;

    sub filename { $_[0]->[0] }
    sub modified { $_[0]->[1] }

    my %last;

    for (`find /tmp -type f 2>/dev/null`) {
      chomp;

      my $dir = dirname $_;
      my $mod = -M $_;

      $last{$dir} = [ basename($_), $mod ]
        if !$last{$dir} || $mod > modified $last{$dir};
    }

    foreach my $dir (sort keys %last) {
      print "$dir: ", filename($last{$dir}), "\n";
    }

    $ ./try
    /tmp: sh-thd-1172576387
    /tmp/exportfig: restorefig.m
    /tmp/shared: .Xdefaults
    /tmp/split-sequence: split-sequence.lisp