if for some reason it's now * vs *.* that's the problem, or you can't just del *.bak at the end due to size constraints, you can loop in a batch file, working with one file at a time so there's never more than 1 .bak file present (the self-calling is because the FOR/DO only allows for running a single command): 
REM foo.bat
@echo OFF
IF "%1" == "process" GOTO processFile
GOTO convertAll

:convertALL
FOR %%f IN (c:\temp\*.txt) DO CALL %0 process "%%f"
GOTO end

:processFile
  SET in=%2
  perl -p -i -e "s/change this/to this/g" %in%
  del %in%.bak
GOTO end

:end

[download]
Update: Oops. fixed the error in variable name in ":processFile" .. also took advantage of "%0" .. thanks ikegami!

In reply to Re: Inplace editing, one liner, without a backup file? by davidrw
in thread Inplace editing, dos one liner, without a backup file? by tphyahoo

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