CreateProcess expects a program and its arguments — not some command for some shell — so ">MyLog.txt" and "2>&1" are being passed to Perl which passes them to your script where you completely ignore them.

What you want is for a cmd shell to execute the string as shell command. That's not gonna happen if you don't run a cmd shell. Executing the following should do the trick:

cmd /c "...the shell command..."
[download]

You could also do the redirection yourself, thus avoiding having to load a shell.

use IPC::Open3 qw( open3 );

open(local *TO_CHLD,     '<', 'nul')       or die;
open(local *FR_CHLD,     '>', 'MyLog.txt') or die;
open(local *FR_CHLD_ERR, '>', 'nul')       or die;

my $pid = open3('<TO_CHLD', '>FR_CHLD', '>FR_CHLD_ERR',
   'C:\AS_v5.8.6_Perl\bin\perl.exe',
   'D:\FinancialReports_PerlSource\PDS\output_test.pl',
);

waitpid($pid, 0);  # To wait for child to finish.
[download]

Update: Added alternative.