replacing the characters in a file

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1

hi
i want to replace the characters between positions 2 to 30 in each line in a file
how to do it
suggestions welcome

2

using Perl:

perl -pi -e 's/(.).{29}(.*)/\1hoohaa\2/' filename

(.) - capture single character (the first character on line)
.{29} - next 29 characters on line
(.*) - capture remaining characters on the line
hoohaa - replacement text
If a line contains less than 30 characters, it remains unaffected

3 
# awk '{ print substr($0,1,1)"replace_string"substr($0,31)}' file