I have 2 fields starting from postion 1 and another from 11.
I may get spaces in between digits (for eg. "5 0 234") and without disturbing them, I need to suppress leading blanks alone. I'm not sure how blank spaces will be there at starting.
The below code I have written replaces all space which I don't want.
Your description is thoroughly confusing. What do you mean by "without disturbing them"? What do you mean by "suppress leading blanks alone"?
You need to do a much better job of describing what it is you want to do before anyone can help you. Show an example of your input records and what you expect for output and explain the rules for getting from input to output.
To get you started, if you had these input records: