open( OUT, ">/tmp/sftp-batch" );
print OUT <<"END";
cd foo
ls
END
close( OUT );

chomp( my @files = `sftp -b /tmp/sftp-batch hostname` );
open(OUT, ">/tmp/sftp-batch-2" );
print OUT <<"END";
cd foo
lcd bar
END
for my $file ( @files ) {
    print OUT "get $file\n";
}

system( "sftp -b /tmp/sftp-batch-2 hostname" );