## Challenge

We get only 45 characters to convert the letters in a string into alternating upper and lower case:

"Hello World! Hallo Welt!"
"HeLlO wOrLd! HaLlO wElT!"

## Solution

A legit 44 character solution which works for all given input:

$_=lc"@ARGV";s/[a-z]/$u^=" ";$&^$u/ige;print
`$_=lc"@ARGV"` is just `$_ = lowercase("#{@ARGV}")`

`print` without argument defaults to `print($_)`

`s/[a-z]/$u^=" ";$&^$u/ige` is $_.gsub!(/[a-z]/)

`$u^=" ";` means switch $u betwen ascii character 0 and ascii character 32 (space) every iteration

`$&^$u` xors with 32, which just so happens to be difference between ascii uppercase and lowercase chars


## Notes

The challenge creator had some interesting comments for us [here](https://github.com/teamavidya/ctf/commit/52f5789e743af94c147d4e5e0fd3796bc162872b#commitcomment-13953040)

Bogbert commented that he had found a 34 character solution!!

print pop=~s/\pL/lc$&^($u^=$")/ger

## Solved by

Original writeup (https://github.com/teamavidya/ctf/tree/master/2015_hacklu/perl_golf%5Bcoding75%5D).