A step on the path to enlightenment

[coolmichael]

To quote an email I just wrote:

I'm quite fond of a command line interface directly to perl:
perl -e "print eval, \"\n\" while(<>);"
which would look nicer in a non-dos shell with better quoting possibilities. And it can be even shorter
perl -p -e "$_=eval"
but then you don't get new lines after each answer.
perl -p -e "s/(.*)/$1/ee"
also works very well, but is longer.

I've never understood s///e very well before, but this just occurred to me while I was writing it. And it worked. I was amazed.

The big question is, why does it work. I don't really know.

--
negativespace.net - all things inbetween.

[Chmrr]

Each /e tacked onto the end is essentially doing another eval. The first eval evaluates $1, which gets it what was matched -- namely, the whole string. The second /e applies eval to what we just got -- the whole string. Thus, it evaluates whatever you typed.

As a side note, you can have your cake and eat it two with your second option -- perl -ple "$_=eval" will give you your newline.

perl -pe '"I lo*`+$^X$\"$]!$/"=~m%(.*)%s;$_=$1;y^`+*^e v^#$&V"+@( NO CARRIER'

[grantm]

perl -p -e "$_=eval"
but then you don't get new lines after each answer

You could use -l to tack on the newlines:

perl -lpe "$_=eval"

[Aristotle]

And of course you can also use -l to shorten any other variants. -n might also be of interest.

perl -le "print eval while <>"
perl -nle "print eval"
perl -ple "$_=eval"

Personally, simply for the sake of clarity, I'd prefer the -n variant.

Makeshifts last the longest.