The general idiom is to use a while loop to iterate over the lines in the file, reading in one line at a time and processing it, then moving on to the next.

Something like this: 

    open FH, "foo" or die "Can't open foo: $!";
    while (<FH>) {
        ## current line is in $_, process it
    }
    close FH or warn "Error closing foo: $!";

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Depending on your situation, you might also want to check out the -p and -n command line flags to perl (perlrun).

If these are files specified on the command line, you can use the special construct: 

    while (<>) {
        ## line is in $_
    }

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This might be useful in a situation like 
    $ process.pl foo.txt bar.txt baz.txt

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to process each of the files on the command line.

In reply to Re: Large file processed line by line by btrott
in thread Large file processed line by line by sdyates2001

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