$ uname -a
CYGWIN_NT-10.0-19044 titan 3.3.5-341.x86_64 2022-05-13 12:27 UTC x86_64 Cygwin

##</code><code>##

#!/usr/bin/env perl

use strict;
use warnings;
use autodie ':all';
use constant {
    OLD => 0,
    NEW => 1,
};

print "OS: $^O; Perl: $^V\n";

my @filenames = 'a' .. 'd';
my %perms = (
    a => [0644, 0644],
    b => [0644, 0755],
    c => [0644, 0440],
    d => [0644, 07644],
);

print "\n*** Initial permissions (visual check):\n";
list_perms(@filenames);
print "\n*** Initial permissions (program check):\n";
check_perms(\@filenames, \%perms, OLD);

change_perms(\@filenames, \%perms, NEW);

print "\n*** Modified permissions (visual check):\n";
list_perms(@filenames);
print "\n*** Modified permissions (program check):\n";
check_perms(\@filenames, \%perms, NEW);

change_perms(\@filenames, \%perms, OLD);

print "\n*** Restored permissions (visual check):\n";
list_perms(@filenames);
print "\n*** Restored permissions (program check):\n";
check_perms(\@filenames, \%perms, OLD);

sub list_perms {
    my (@files) = @_;
    my @cmd_list = (ls => '-l', @files);
    CORE::system {$cmd_list[0]} @cmd_list;
    return;
}

sub check_perms {
    my ($files, $perms, $oldnew) = @_;

    for my $file (@$files) {
        my $perm = (stat $file)[2] & 07777;
        my $expected
            = sprintf('%#5o', $perms->{$file}[$oldnew]);

        print
            "File: '$file'; Perm: ",
            sprintf('%#5o', $perm),
            '; Check: ',
            (
                $perm == $perms->{$file}[$oldnew]
                ? 'OK' : "WRONG (expected: $expected)"
            ),
            "\n";
    }

    return;
}

sub change_perms {
    my ($files, $perms, $oldnew) = @_;

    for my $file (@$files) {
        chmod $perms->{$file}[$oldnew], $file;
    }

    return;
}

##</code><code>##

$ ./perm_tasks.pl
OS: cygwin; Perl: v5.36.0

*** Initial permissions (visual check):
-rw-r--r-- 1 ken None 0 Sep  4 02:07 a
-rw-r--r-- 1 ken None 0 Sep  4 02:07 b
-rw-r--r-- 1 ken None 0 Sep  4 02:07 c
-rw-r--r-- 1 ken None 0 Sep  4 02:16 d

*** Initial permissions (program check):
File: 'a'; Perm:  0644; Check: OK
File: 'b'; Perm:  0644; Check: OK
File: 'c'; Perm:  0644; Check: OK
File: 'd'; Perm:  0644; Check: OK

*** Modified permissions (visual check):
-rw-r--r-- 1 ken None 0 Sep  4 02:07 a
-rwxr-xr-x 1 ken None 0 Sep  4 02:07 b
-r--r----- 1 ken None 0 Sep  4 02:07 c
-rwSr-Sr-T 1 ken None 0 Sep  4 02:16 d

*** Modified permissions (program check):
File: 'a'; Perm:  0644; Check: OK
File: 'b'; Perm:  0755; Check: OK
File: 'c'; Perm:  0440; Check: OK
File: 'd'; Perm: 07644; Check: OK

*** Restored permissions (visual check):
-rw-r--r-- 1 ken None 0 Sep  4 02:07 a
-rw-r--r-- 1 ken None 0 Sep  4 02:07 b
-rw-r--r-- 1 ken None 0 Sep  4 02:07 c
-rw-r--r-- 1 ken None 0 Sep  4 02:16 d

*** Restored permissions (program check):
File: 'a'; Perm:  0644; Check: OK
File: 'b'; Perm:  0644; Check: OK
File: 'c'; Perm:  0644; Check: OK
File: 'd'; Perm:  0644; Check: OK

##</code><code>##

Cygwin                         MSWin
=============================  ====================
/cygdrive/c                    C:\
/cygdrive/d                    D:\
/cygdrive/c/Users/ken          C:\Users\ken
/cygdrive/c/cygwin64           C:\cygwin64
/                              C:\cygwin64
/cygdrive/c/cygwin64/home/ken  C:\cygwin64\home\ken
/home/ken                      C:\cygwin64\home\ken