in reply to greping thru a hash of arrays

You can grep through it, but you have an error in how you are accessing the array ref. You need to do it like this: 
if (grep /$_/,  @{$tbl{$i}}  ) {

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Update: Removed square brackets which I didn't see the first time around.

Another problem, though, is that $_ gets assigned to in the grep operation, and that the match operator implicitly operates on $_. Thus, grep /$_/, ... is equivalent to grep { $_ =~ /$_/ } (...) which is probably not what you want. Instead, try this: 

while (my $line = <IN>) {
  ...
  for my $i (...) {
    if (grep /$line/, @{$tbl{$i}}) {
      ...
    }
  }
}

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Re^2: greping thru a hash of arrays
by pglenski (Beadle) on May 20, 2008 at 21:10 UTC
    Thanks, that works. But why?
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      grep /$_/, [ @{$tbl{$i}} ]

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      means:
      Dereference the array-Ref in $tbl{$i}, make a reference to an anonymous array ( [ ] ) from the resulting list and grep through a list with a single item: the single reference to the anonymous array.

      @tbl{$i} is btw. wrong, see this example : 
      $perl
 perl 
use strict;
use warnings;

my %hash;
$hash{a} = [ 1,2 ];

print "@hash{a}", $/;
Scalar value @hash{a} better written as $hash{a} at - line 7.

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      edit: several updates/corrections due to some misleading thoughts while typing too fast

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      There were a few errors. As linuxer pointed out, the second argument to grep should not be an array-ref. The second through last arguments are the list of items to grep through.

      Also, instead of @tbl{$i} you want to use @{$tbl{$i}}.

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