$ touch a

$ perl -MFile::stat -wle'print "".localtime( stat("a")->ctime )'
Fri Aug 21 13:31:40 2009

$ sleep 2

$ perl -MFile::stat -wle'print "".localtime( stat("a")->ctime )'
Fri Aug 21 13:31:40 2009

$ chmod go= a

$ perl -MFile::stat -wle'print "".localtime( stat("a")->ctime )'
Fri Aug 21 13:32:25 2009