Here is a simple regular expression to convert a string

while (<DATA>) {
    s/(\d+)\/(\d+)\/(\d+)\s+(\d+):(\d+):(\d+)\s+(PM|AM)/$3.'-'.$1.'-'.
+$2.'-'.($7 eq 'PM'?($4+12):$4).'.'.$5.'.'.$6.'.0000'/ge;
     print $_;
}

__DATA__
ID,21,11814,1,11989,150,Y,10/25/2012 11:36:25 AM,TEST
ID,22,11814,1,11989,150,Y,10/25/2012 11:36:25 PM,TEST
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Output:
ID,21,11814,1,11989,150,Y,2012-10-25-11.36.25.0000,TEST
ID,22,11814,1,11989,150,Y,2012-10-25-23.36.25.0000,TEST