How can I swap some values in a string variable and write it back with new values using Free Pascal?

Having read a line from a text file using ReadLn(InputFile, strVar), I need to read each character of strVar, and if it contains the letter 'E' (for example), I want to output (write to a new file, in fact) the original variable but with the 'E' being swapped\replaced with the numeric digit '3'.

So, if '开发者_如何学PythonExample' is read from the file, I want '3xample' to be written to a new file.

How do I code the swapping in Free Pascal (I can do the writing to the file bit)? Other languages seem to have a swap function or something.

Thanks

Ted

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You can use StringReplace

strVar := StringReplace(strVar, 'E', '3', [rfReplaceAll]);