unless (open(FILE,">temp")) {
   warn "error";
    $x=1;
}
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unless (open(FILE,">temp")) {

This is fine and dandy. I used to prefer it. But, it should come with a caveat... If you like to autovivify your filehandles, using that construct might cause a problem. Consider:

unless (open my $fh, '<', 'file') { 
    # . . .
}
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In that code, $fh is lexical to the unless block. That probably isn't what you want because you only enter the block if the open fails. This pitfall may be more likely to come up when changing existing code than when writing new code altogether.

You can get around it by declaring $fh prior to the unless but, now anyway, I prefer to avoid it by using

open my $fh, '<', 'file' or do { 
    # . . . 
};
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instead. That also puts the emphasis back on the open statement itself.

-sauoq
"My two cents aren't worth a dime.";

I know 'unless' is the right *perl* way to do that, but I've never quite gotten used to using 'unless'. I prefer to use 'if not' in place of 'unless' - it just makes more sense to me:

  if (not open(FILE, ">temp")) {
     warn "error";
     $x = 1;
  }
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HTH.

open(FILE,">temp") or warn "error message" and $x = 1;
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Or, if you don't feel a need to use one line:

open(FILE,">temp") or $x = 1;
$x and warn "error message";
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Or, do what dreadpiratepeter said to, if you want to be absolutely clear. :)

- Matt Riffle
  Sr. Systems Programmer, pair Networks, Inc.
  (although, I speak only for myself; code is untested unless otherwise stated)

open (FILE,">temp") or $x=1, warn "error message"

open (FILE, '>', "temp") or do { warn "error message"; $x=1 };
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I'd probably do something like this:

my $x;
open (FILE, ">temp") || do {
   warn "error message";
   $x = 1;
};
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...but then $x is still undefined outside the do{} block (which may or may not be a problem).

my $x;
open (FILE, ">temp") || do {
   warn "error message";
   $x = 1;
}
print "\$x is $x";
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dave

You're right but (as you mentioned) the fact that $x is undefined may not be a problem at all.

my $x;
open (FILE, ">temp") || do {
   warn "error message";
   $x = 1;
};
if ($x) {
   # so something
}
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-- vek --

Ooops sorry, my bad. Please ignore the above.

dave

open(FILE,">temp") || (warn "error message" and ($x = 1));
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This is dangerous:

open(FILE,"<temp") || (($x = 1) && warn "error message1: $x");
open(FILE,"<temp") || (($x = 0) && warn "error message2: $x");
__END__

error message1: 1 at test-a.pl line 1.
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