C:\>ls -l pid.txt
-rw-rw-rw-   1 user     group           4 Sep 15 16:51 pid.txt

C:\>type pid.txt
8748
C:\>perl -lwe "print(':'.localtime((stat 'pid.txt')[10]))"
:Thu Sep 15 16:45:56 2011

C:\>del pid.txt

C:\>echo 8748 >pid.txt

C:\>perl -lwe "print(':'.localtime((stat 'pid.txt')[10]))"
:Thu Sep 15 16:45:56 2011