Git doesn't detect change, if file modification time is restored to original one

I wrote a search & replace perl script, which recursively searches files and replaces text in them. After replace, it restores original modification time (mtime) of file.

Interesting, that git status doesn't show replaced changes, if the mtime is same as original.

Is there a way to force git status to show changes, even if the file dates are the same?

I tried to set core to:
    trustctime = false
    checkStat = minimal
Unfortunately the change is still not detected :(
It seems isn't a way to force fallback to file checking and completely
ignore file modification date :(

Any idea?

Thanks, Konrad Lorinczi