I guess that $^I only works if you use the magic ARGV file handle, so you could try something along these lines: 
sub replace {
    local $^I = '';
    local @ARGV = ($para);
    while(<>) {
        s/UI_EM/$newpar/g;
        print;
    }
}

[download]

(Untested)

In reply to Re: $^I why this symbol does not work ? by moritz
in thread $^I why this symbol does not work ? by kingwrcy

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