# write.pl

my $pid = fork;
if($pid == 0) {
    sleep 5;
    system('echo "hello world" > foo.txt');
} 

##</code><code>##

# copy.pl

my $test = system('perl', 'write.pl');

my $file1 = 'foo.txt';
my $status = system("cp $file1 file2");

##</code><code>##

$ perl -w copy.pl
cp: cannot stat `foo.txt': No such file or directory

##</code><code>##

# copy2.pl

use strict;
 
my $test = system('perl', 'write.pl');

my $file1 = 'foo.txt';

while(1) {
    last if -e $file1 && ! qx/lsof $file1/;
} 
my $status = system("cp $file1 file2");