2 possibilities come to my mind at the moment:

If the file paths are not too long, you can pass them as additional parameters to system:

# master

my @files = qw[ path/to/file0 path/to/file1 path/to/file2 ];
system 'perl', 'slave.pl', @files;
[download]

# slave

print "List of files to process:\n";
print "    $_\n" for (@ARGV);
[download]

If the paths are too long to pass them all as parameters, write them to a file, 1 per line:

# master

my @files = qw[ path/to/file0 path/to/file1 path/to/file2 ];
open my $fh, '>', 'filelist';
print $fh, "$_\n" for (@files);
close $fh;
system 'perl', 'slave.pl'
[download]

# slave

open my $fh, '<', 'filelist';
print "List of files to process:\n";
print while <$fh>;
close $fh;
[download]