How to create substrings from input string using regex? -

how create substrings input string using regex?
each substring should have 3 contigious characters in input.

ex:

 input text="1234abc"; 

expected substring

output :123,234,34a,4ab.abc....

use lookahead

 (?=(.{3})) 

so,first 3 characters captured in group within lookahead..now move next character (i.e 2 in example) , again capture 3 characters , on..

note:

group captures within lookaround support limited regex implementations