#!/usr/bin/env perl -w
use strict;

my $foo = qx{ ls }; # alternate syntax for backticks
open my $fh, '>', 'bar.out' or die $!; 
print $fh $foo;
close $fh;
__END__

##</code><code>##

$ cat bar.out
foo.pl
$

##</code><code>##

#!/usr/bin/env perl -w
use strict;

my $foo = qx{ ls baz }; # doesn't exist
open my $fh, '>', 'bar.out' or die $!; 
print $fh $foo;
close $fh;
__END__

##</code><code>##

$ cat bar.out
$

##</code><code>##

#!/usr/bin/env perl -w
use strict;

my $foo = qx{ ls baz 2>&1 };
open my $fh, '>', 'bar.out' or die $!;
print $fh $foo;
close $fh;
__END__

##</code><code>##

$ cat bar.out 
ls: baz: No such file or directory
$