Windowscmd.exe does not use' as string delimiters, only". What you're doing is equivalent to:

perl -p -i.bak -e "'s/log/log,XYZ/g'" config.txt

so-w is complaining "you gave me a string but it does nothing".

The solution is to use double quotes instead:

perl -p -i.bak -e "s/log/log,XYZ/g" config.txt

or to simply leave them off, since there's no metacharacters in this command that would be interpreted bycmd.exe.

Addendum

cmd.exe is just a really troublesome beast, for anybody accustomed tosh-like shells. Here's a few other common failures and workarounds regardingperl invocation.

@REM doesn't work:perl -e"print"@REM works:perl -e "print"@REM doesn't work:perl -e "print \"Hello, world!\n\""@REM works:perl -e "print qq(Hello, world!\n)"

ephemient's answer summarizes the problem well, but you do have another option: change your shell fromcmd.exe to a better shell. If you are a Unix type person then I would suggest looking intoCygwin which provides the sort of environment you are used to (for example,Bash and GNU utilities).

If you are a Windows-type person I would suggest looking atPowerShell (née MSH née Monad). In fact, I would suggest looking into PowerShell even if you are Unix type person. It integrates with.NET and has many neat features (like objects being passed through pipes rather than simple lines of text). If I were stuck on a Microsoft OS, it is the shell I would be using.

Other shells for Windows that people seem to like:

• UWIN
• MinGW
• UnixUtils
• Microsoft Windows Services for UNIX (SFU)
• MKS Toolkit

• windows
• perl