Perl 5
while <STDIN> { ...

In Perl 5, the parens are not optional. And please use a monospaced font for code :).

dot/underscore
String Concatenation from . to _. Note: whitespace is neccessary.

Only if there's a \w character next to it. $foo{bar}_$foo{bar} will be possible, but $foo_$bar will not (or at least not DWIM).

'for' is now a shortcut for 'foreach'.

I don't know if shortcut is the right word, but currently, for and foreach are exactly the same. That is, foreach (EXPR;EXPR;EXPR) and for (LIST) work.

2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$
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