for(a..z) { print }
for(a...z) { print }    # the same!

while(<>) { print if 1..5 }
while(<>) { print if 1...5 }    # the same!

This is useful if you want to do things like "get the lines between
lines starting with the same digit (character, substring, regexp or
whatever)" as in this mini example:

while(<DATA>) {
  chomp();
  my $seq_numb = $_ =~ /^(1|2|3)/ ... /^$1/;
  if ($seq_numb ne "" and
      $seq_numb > 1   and
      $seq_numb !~ /E0$/) {
    print "Sequence Number: $seq_numb",
          " Matched String: $_", "\n";
  }

This should print:
Sequence Number: 2 Matched String: aaa
Sequence Number: 3 Matched String: aab
Sequence Number: 2 Matched String: ccc
Sequence Number: 3 Matched String: ccd
Sequence Number: 4 Matched String: cce
Sequence Number: 2 Matched String: eee

    $ perl -wle 'for (qw /foobar barbar bazbar/) {print}' |\
      perl -wne 'print if /foo/ ..  /bar/'
    foobar
    barbar
    $ perl -wle 'for (qw /foobar barbar bazbar/) {print}' |\
      perl -wne 'print if /foo/ ... /bar/'
    foobar
    $

Abigail
--
perl -e '* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / /
         % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % %;
         BEGIN {% % = ($ _ = " " => print "Just Another Perl Hacker\n")}'

[pigment.dircon.net] $ perl -e 'while(<>) { print if (/foo/ ... /bar/) }'
foo hfgfg bar
foo hfgfg bar
uryjh
uryjh
[pigment.dircon.net] $ perl -e 'while(<>) { print if (/foo/ .. /bar/) }'
foo hfgfh bar
foo hfgfh bar
dhjdh

       In scalar context, ".." returns a boolean value.  The
       operator is bistable, like a flip-flop, and emulates the
       line-range (comma) operator of sed, awk, and various
       editors.  Each ".." operator maintains its own boolean
       state.  It is false as long as its left operand is false.
       Once the left operand is true, the range operator stays
       true until the right operand is true, AFTER which the
       range operator becomes false again.  (It doesn't become
       false till the next time the range operator is evaluated.
       It can test the right operand and become false on the same
       evaluation it became true (as in awk), but it still
       returns true once.  If you don't want it to test the right
       operand till the next evaluation (as in sed), use three
       dots ("...") instead of two.)  The right operand is not
       evaluated while the operator is in the "false" state, and
       the left operand is not evaluated while the operator is in
       the "true" state.  [...]

Here's my test:

    for (qw(none leftright none right none)) {
      printf "%20s .. %3s ... %3s\n", $_,
        (scalar (/left/../right/) ? "YES" : "NO"),
        (scalar (/left/.../right/) ? "YES" : "NO");
    }

And the results:

                none ..  NO ...  NO
           leftright .. YES ... YES
                none ..  NO ... YES
               right ..  NO ... YES
                none ..  NO ...  NO

And that looks correct... the /right/ on the "..." didn't test on
the same line as the /left/ did... it had to wait further.

I'm not sure how Abigail got those results.

     $ perl -wle 'for (qw /foobar barbar bazbar/) {print}' |\
       perl -wne 'print if /foo/ ..  /bar/'
     foobar
     barbar
     $ perl -wle 'for (qw /foobar barbar bazbar/) {print}' |\
       perl -wne 'print if /foo/ ... /bar/'
     foobar
     $

Because I get exactly the opposite when I run my 5.5.3 Perl against
that code!  Abigail, what Perl are you running?

print "Just another Perl hacker,"

5.005_03. I used cut-and-paste, then yank-and-copy, and removed the
'.' on the wrong line. My post should have read:

        $ perl -wle 'for (qw /foobar barbar bazbar/) {print}' |\
          perl -wne 'print if /foo/ ... /bar/'
        foobar
        barbar
        $ perl -wle 'for (qw /foobar barbar bazbar/) {print}' |\
          perl -wne 'print if /foo/ ..  /bar/'
        foobar
        $

Abigail
--
sub f{sprintf'%c%s',$_[0],$_[1]}print f(74,f(117,f(115,f(116,f(32,f(97,
f(110,f(111,f(116,f(104,f(0x65,f(114,f(32,f(80,f(101,f(114,f(0x6c,f(32,
f(0x48,f(97,f(99,f(107,f(101,f(114,f(10,q ff)))))))))))))))))))))))))