Regular Expression Replace in Notepad++

Notepad++ can search strings and replace them using regular expression
Regular_Expression (Wikipedia)
it can be use to :-
1. generate a huge list of mapflags
2. fix outdated format on the script commands
3. apply a quick fix on CVS style database
4. convert client side item list into array

Example 1. Generate a huge list of mapflags

1. goto db/map_index.txt, copy over the map list

2. there are some lines commented, so find the line with // and remove them by doing this
Find with regular expression^//[a-z0-9_@-]*$ Replace with empty string, this effectively leave the line blank

3. Edit -> Line Operations -> Remove Empty lines

4. Find with regular expression^//([a-z0-9_@-]*)$ Replace with \1 mapflag nobranch

Example 2. Fix outdated format on the script commands

Find with regular expressionpow.(([ 0-9]*),([. a-z0-9_@-]*).) Replace with \(\2**\3\)

Example 3. Apply a quick fix on CVS style database

rathena only, Hercules has switched to libconfig format
goto db/re/item_db.txt

Find with regular expression ^([0-9]*),([^,]*),([^,]*),4, Replace with \1,\2,\3,99, Find with regular expression ^([0-9]*),([^,]*),([^,]*),5, Replace with \1,\2,\3,4, Find with regular expression ^([0-9]*),([^,]*),([^,]*),99, Replace with \1,\2,\3,5,

Example 4: Convert client side item list into array

goto kro/data/cardprefixnametable.txt

Find with regular expression ([0-9]+)#([][&0-9a-z_'.()]*)# Replace with $@cardprefix$[\1] = "\2";

External Links:

Disable dead branch (Example 1) 
Convert pow(a,b) into a**b (Example 2)
Swap item type IT_ARMOR and IT_WEAPON (Example 3)
getitemname2 function (Example 4)