bash$ ls
junk
test.junk

bash$ ls | sed 's/\./-.-/'  # piping between GNU utils works
junk
test-.-junk

bash$ ls > junk

bash$ perl -pe 's/\./-.-/' junk  # perl reading from a file works
junk
test-.-junk

bash$ perl -pe 's/\./-.-/' < junk # redirecting stdin from file works
junk
test-.-junk

bash$ ls | perl -pe 's/\./-.-/'  # using a pipeline
# nothing comes out

# trying the pipe again, more carefully this time:

bash$ ls | perl -e 'while (<>) {
> s/\./-.-/;
> print;
> }
> print "all done\n";'
all done