$ echo "foo foo foo foo" | sed 's/foo/bar/3'
foo foo bar foo
$ perl6 -pe 'next if ++$ == 2' example.txt
... prints all lines except line 2.
This is an example from Perl 6 One Liners[1].
The `$` is just just an unnamed variable that is getting incremented once per evaluation (-e is for `evaluate`) which in this case happens once per line (-p is for printing each line of input after eval'ing the code -- unless a `next` applies, in which case that line gets skipped).
And...
$ echo "foo foo foo foo" | perl6 -pe 's:3rd/foo/bar/'
... replaces the third foo with bar.
P6 regexes are far easier to read and way more powerful than P5 regexes. The `:3rd` bit is a general language feature called "Adverbs", in this case applied to the regex focused s/// built in.[2]
Quote:
"I asked on a forum what the goals are for relative size and speed of Perl 6 vs. Perl 5, and a Perl 6 developer responded that a reasonable goal would be to have Perl 6 be twice as big as Perl 5 and take twice as long to start up.
"To achieve this goal, the Perl 6 developers will have to shrink the program size by a factor of 6.1 (that is, get rid of about 84% of the code.) They'll need to reduce startup memory consumption by a factor of 13.7 (that is, cut out 93.7% of their memory use) and reduce startup time by a factor of over 275.
"Oh, and this is after they add in all the missing features required to bring Perl 6 up to production-level."
Has the situation gotten better since 2010?
Not really. Startup uses about the same RAM. It's about 10x faster.
The best docs I know about performance would be http://pmichaud.com/2012/pres/yapcna-perflt/slides/slide17.h... and http://jnthn.net/papers/2014-yapceu-performance.pdf#page=72
> "... all the missing features required to bring Perl 6 up to production-level."
The latest story is that the last major missing features (Unicode grapheme-by-default and native arrays) will land in the next few months and Perl 6 will be declared "officially ready for production use" by the end of 2015.
sed: sed -n '4!p'
awk: awk 'NR != 4'
perl: perl -ne '$. != 4 && print'
Not much between them really.