$ perl -e 'while(true){print"line? >";$line=<STDIN>;chomp $line;print $line," world\n"}'
line? >line1
line1 world
line? >sttw  rtztrw
sttw  rtztrw world
line? >last line..............
last line.............. world
line? > world
line? > 

$ perl -e 'print "@ARGV"," world\n" if $ARGV[0] || do {while(true){print"line? >";$line=<STDIN>;chomp $line;print $line," world\n"}}' "reverse(dlrow) is"
reverse(dlrow) is world