regex101: super cool

Positive Lookbehind(?<=\s)

\sany whitespace character

Group start(?<start>%%)?

?repeats the group contents below at most once:

%%the literal text %%

%dMODIFIER_PROPERTY_the literal text %dMODIFIER_PROPERTY_ (case sensitive)

Group 2(\w+)

\w+any word character, repeated at least once

%the literal % (37₁₀ / 45₈ / 25₁₆)

Condition(?(start)|%%)

Uses the first branch if group start matched

If the condition is true, match this branch: — matches an empty string

Otherwise, match this branch:%%

%%the literal text %%

Positive Lookahead(?=[^%]|$)

1st Alternative[^%]

Negated Character Class[^%]

%the literal % (37₁₀ / 45₈ / 25₁₆)

2nd Alternative$

$end of line

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Search reference

Regular Expression

(?<=\s)(?<start>%%)?%dMODIFIER_PROPERTY_(\w+)%(?(start)|%%)(?=[^%]|$)

New

"DOTA_Tooltip_modifier_viper_poison_attack_slow_Description"	"Velocidad de movimiento reducida un %dMODIFIER_PROPERTY_MOVESPEED_BONUS_PERCENTAGE%%%, resistencia mágica reducida un %dMODIFIER_PROPERTY_MAGICAL_RESISTANCE_BONUS%%%. Recibiendo daño a lo largo del tiempo."
%%%dMODIFIER_PROPERTY_SOMETHING%
%%dMODIFIER_PROPERTY_SOMETHING%
%%%%dMODIFIER_PROPERTY_SOMETHING%
%%%dMODIFIER_PROPERTY_SOMETHING%%
%%%dMODIFIER_PROPERTY_SOMETHING%%%
%dMODIFIER_PROPERTY_SOMETHING%
%dMODIFIER_PROPERTY_SOMETHING%%
%dMODIFIER_PROPERTY_SOMETHING%%%
%dMODIFIER_PROPERTY_SOMETHING%%%%