Ok I lied, there is a difference between the longhand perl while (<>) { } statement and -n: you can't use next or last to exit the loop - however you can use BEGIN{ } and END { } blocks to get pre and post loop code, run a text file containing some numbers through this baby:
perl -l -n -e 'BEGIN{$sum=0;} $sum=$sum+ $1 if /(\d+)/;print $1; END {
+print "Total: ",$sum}'
You were right the first time. There really is no difference. Why don't
next and
last work for you?
echo -e "a\nb\nc" | perl -lne 'next if /b/; print'
a
c
echo -e "a\nb\nc" | perl -lne 'last if /b/; print'
a
In fact, it is equivalent to
LINE: while (defined($_=<ARGV>)) { ... }
which means that you can do
next LINE if you have a loop within your one-liner.
Two other comments: I use the canonical
perl -lne 'print $s += $1 if /(\d+)/'
for summing numbers. For one-liners, it's much less typing, and gives you pretty much everything you need: the total sum, and a running sum that still allows you to catch errors.
And finally, the one big missing piece in this tutorial is that it is absolutely necessary, for reasons of tradition, to at least try to make your options spell out words. So never use -alne when -lane would work.
