If you want to escape the spaces in the string of an array.You try the following,

my %hash=(1=>"one");
my $str='C:/Program Files/Perl Express/sample.txt';
$str=~s/ /\\ /g;
@ARGV = ($str,%hash);
system("./script.pl @ARGV");
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In the script.pl,I printed the array @ARGV. It printed the Path and hash keys and values correctly.