(Guildenstern) REx6: Populating a Hash: Can someone help me to understand?

Okay. I think I see what you're trying to do now. Based on what I see in the Cookbook on p 140, it looks like you want a hash whose values are array refs. This will effectively get you the "more than one value per hash key" that you're looking for. It is kind of hard to tell what to help you with regarding that particular example without a little smaller target for us to aim for.
The example is fairly simple, except for the fact that instead of assigning values to an array, then setting the array reference to a hash key, it pushes values directly into the hash.
BTW: here is the code I'm referring to:

%ttys = ();

open(WHO,"who|") or die "can't open who: $!";
while (<WHO>) {
  ($user, $tty) = split;
  push( @{$ttys{$user}}, $tty);
}

foreach $user (sort keys %ttys) {
 print "$user: @{$ttys{$user}}\n";
}
[download]

The one line that looks like it might cause understanding problems is push( @{$ttys{$user}}, $tty); Basically, push expects a list for its forst argument, but $ttys{$user} will return a list refernce, not a list. Using @{...} forces push to evaluate what's in those braces as a list, which it knows how to work with.

Guildenstern
Negaterd character class uber alles!

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RE: (Guildenstern) REx6: Populating a Hash: Can someone help me to understand? by tye (Sage) on Sep 19, 2000 at 20:50 UTC
I find that removing the autovivication can make the code easier to understand (and I wish there was a way to force this): `my %ttys= (); open( WHO, "who\|" ) or die "Can't fork to read from who: $!"; while( <WHO> ) { my( $user, $tty )= split; if( ! exists $ttys{$user} ) { $ttys{$user}= [$tty]; } else { push @{$ttys{$user}}, $tty; } } foreach my $user ( sort keys %ttys ) { print "$user: @{$ttys{$user}}\n"; }` [download] The `if` shows a bit of what happens under the covers in the previous example. - tye (but my friends call me "Tye")	[reply] [d/l] [select]
(Guildenstern) REx8(!): Populating a Hash: Can someone help me to understand? by Guildenstern (Deacon) on Sep 19, 2000 at 20:58 UTC
I whole heartedly agree, but that code was taken verbatim from the Perl Cookbook, so it's easy to see how someone with little to no experience using references could be confused by that code. About the time you get a handle on \@, somebody throws @{...} at you? Ack! Also, I understand that the book's just full of examples, but shouldn't they at least make an effort to at least pass strict? Guildenstern Negaterd character class uber alles!	[reply]