Perl Programming/Keywords/-M
The -M keyword
edit-M is a file test that returns the script start time minus file modification time, in days.
It takes one argument, either a FILENAME, a FILEHANDLE, or a DIRHANDLE to test the associated file to see, if something is true about it. If the argument is omitted, it tests $_. -M returns 1 for true and an empty string for false. If the file doesn't exist or can't be examined, it returns undef and sets $! (errno).
Syntax
edit -M DIRHANDLE
-M EXPRESSION
-M FILEHANDLE
-M FILENAME
-M