utime(2) - perldoc - phpman

    utime LIST
            Changes the access and modification times on each file of a list
            of files. The first two elements of the list must be the NUMERIC
            access and modification times, in that order. Returns the number
            of files successfully changed. The inode change time of each
            file is set to the current time. For example, this code has the
            same effect as the Unix touch(1) command when the files *already
            exist* and belong to the user running the program:

                #!/usr/bin/perl
                my $atime = my $mtime = time;
                utime $atime, $mtime, @ARGV;

            Since Perl 5.8.0, if the first two elements of the list are
            "undef", the utime(2) syscall from your C library is called with
            a null second argument. On most systems, this will set the
            file's access and modification times to the current time (i.e.,
            equivalent to the example above) and will work even on files you
            don't own provided you have write permission:

                for my $file (@ARGV) {
                    utime(undef, undef, $file)
                        || warn "Couldn't touch $file: $!";
                }

            Under NFS this will use the time of the NFS server, not the time
            of the local machine. If there is a time synchronization
            problem, the NFS server and local machine will have different
            times. The Unix touch(1) command will in fact normally use this
            form instead of the one shown in the first example.

            Passing only one of the first two elements as "undef" is
            equivalent to passing a 0 and will not have the effect described
            when both are "undef". This also triggers an uninitialized
            warning.

            On systems that support futimes(2), you may pass filehandles
            among the files. On systems that don't support futimes(2),
            passing filehandles raises an exception. Filehandles must be
            passed as globs or glob references to be recognized; barewords
            are considered filenames.

            Portability issues: "utime" in perlport.