#!/usr/bin/perl -w

use Benchmark;

my $filename = "test.txt";

sub file_open {
        open (FILE, ">$filename");
        close FILE;
}

sub utime1 {
        my $current_time = time();
        utime($current_time, (stat($filename))[9], $filename);
}

sub utime2 {
        my $current_time = time();
        utime($current_time, $current_time, $filename);
}

timethese(500000, {
        'openfile' => \&file_open,
        'utime1' => \&utime1,
        'utime2' => \&utime2
});

Benchmark: timing 500000 iterations of openfile, utime1, utime2...
  openfile: 32 wallclock secs (19.46 usr + 11.91 sys = 31.37 CPU)
    utime1: 18 wallclock secs (11.93 usr +  5.75 sys = 17.68 CPU)
    utime2:  7 wallclock secs ( 3.92 usr +  3.03 sys =  6.95 CPU)