Select Code to Download

   perl -ple "BEGIN{open $to,'>',shift @ARGV;select $to}" destination.
+txt source1.txt source2.txt

perl -ple "BEGIN{open $to,'>',shift @ARGV and select $to if $ARGV[0]}"

...

# to file
perl -ple "BEGIN{open $to,'>',shift @ARGV and select $to if $ARGV[0]}"
+ dst src1 src2

perl -ple "BEGIN{open $to,'>',shift @ARGV and select $to unless $ARGV[
+0] eq 'STDOUT'}"

...
perl -ple "BEGIN{open $to,'>',shift @ARGV and select $to unless $ARGV[
+0] eq 'STDOUT'}" STDOUT src1 src2