Align lines by an arbitrary regexp. For emacs regexp docs see:
https://www.cs.elte.hu/local/texinfo/emacs/emacs_16.html#SEC85

Emacs regexps are quite different from Perl regexps. Many of the \x
constructs exist in both, but have totally different meanings. Oddly,
isearch-forward-regexp seems to interpret regexps differently than
query-replace-regexp. The isearch variant seems to be greedy, whereas
the default elsewhere is non-greedy matching. There doesn't seem
to be an override for the non-greedy, although in many cases there
will be workarounds.


To align region and simultaneously set the aligning regexp use:

align-regexp


Align a new region with the existing align-regexp:

align-entire


Un-align by doing a query-replace-regexp with a string. For example replace  "\s += " with " = ".

Emacs doesn't seem to understand octal e.g. \040 is space. Enter chars with ^q 
and the character you need. 

There are syntax classes, used with \s 

whitespace \s  \s-
word \sw
symbol \s_
punctuation \,
parenthesis \s( \s) (may match {} [] {})
quote \s"
escape \s\
character quote \s/
comment start \s<
comment end \s>
generic comment delimiter \s!
generic string delimiter \s|


Use registers instead of a clipboard
Regitsters are named with a single character. Letters work, and apparently
do carriage return, etc.

copy region to register a

C-x r x a

Instert register a

C-x r i a

You can use the registers numerically i.e. for a counter
in a keyboard macro.

Position the cursor on a number. Copy the number into register a

C-x r n a

Increment the number in register a

C-x r + a

C-x r +		increment-register
C-x r n		number-to-register
C-x r g		insert-register
C-x r i		insert-register
C-x r x		copy-to-register
C-x r s		copy-to-register



Indent values aligned like this:

$cspecies{"ARABIDOPSIS"} = 	  6;
$cspecies{"DROSOPHILA"} = 	  44;
$cspecies{"E_COLI"} = 		  4;

Assuming all the values are in the column right after
the equal sign and you want to indent to column 34.

search "="
esc-X
indent-to-column
34
control-N
control-A