in reply to Need help understanding code snippet with "grep -f"

My guess what this does is:

Don't guess, read the docs, grep is not like grep, grep is like foreach that filters out wanted list items

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Re^2:Need help understanding code snippet with "grep -f"
by fifaltra (Acolyte) on Dec 23, 2015 at 04:09 UTC
    Well, I did read it, but I couldn't figure out what the -f does there, and how the behaviour of grep described in the docs would give me a list of existing files. But that's probably cleared up now. Is there also documentation on this "-f" thing? Because it's really hard to google for something as short as "-f"...

      Reading this reminded me .. I had the exact same thing trip me up. -f is not a switch to the grep function but rather an independently defined function that just happens to be used as an argument here. But the unix-familiar mind sees that and thinks "grep -f" is a special form of "grep" and seeks the answer in the grep documentation. And doesn't find it.

      Using the block form of grep might have made this clearer.

      @files = grep { -f } glob("~/data/*");
      But God demonstrates His own love toward us, in that while we were yet sinners, Christ died for us. Romans 5:8 (NASB)