greenhorn has asked for the wisdom of the Perl Monks concerning the following question:

It was here that I saw recently how $/ could be temporarily redefined within a block. For example:

{
   local $/ = '';
   chomp(@array = <FILEHANDLE>);
}

[download]

I thought I would shorten it slightly:

{
   local $/;
#  ( or:  local undef $/;  )
   chomp(@array = <FILEHANDLE>);
}

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This made a considerable difference in the contents of "@array". In the first case<KBD> (local $/ = '';) </KBD>entire paragraphs were slurped into each element of the array. But in the second<KBD> (local $/;) </KBD> this didn't happen; each element within the array was a single line from the input file.

How is it that<kbd style=color:red> '' </kbd>is so different from no value (or so different from "undef")?

Replies are listed 'Best First'.
Re: Altering the value of
by plaid (Chaplain) on Jul 03, 2000 at 05:14 UTC
    From the perlman:perlvar page 
    Works like awk's RS variable, including treating empty
lines as delimiters if set to the null string.
...
You may set it to a multi-character string to match a
multi-character delimiter, or to undef to read to end of
file.

    [download]
    The values of '' and undef both have pre-defined meanings in the context of the $/ variable.
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[d/l]
Re: Altering the value of
by davorg (Chancellor) on Jul 03, 2000 at 11:59 UTC

    The point is that all three behaviours (line-by-line, paragraph-at-a-time and all-in-one) all have their uses in solving different problems, so those nice Perl5 Porters have given us the flexibility to use all three (and a whole bunch more by setting $/ to the appropriate value).

    As plaid notes, this is all explained in perlman:perlvar.

    --
    <http://www.dave.org.uk>

    European Perl Conference - Sept 22/24 2000
    <http://www.yapc.org/Europe/>
[reply]
      > the flexibility to use all three

      As usual, there's a ton more to this than I have imagined...thanks, genn'lmen.

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