in reply to Selecting particular key-value pairs in hashes

Simply test the keys against your pattern: 

foreach my $key ( keys %hash )
{
    if( $key =~ m/\d+_\d+/ )
    {
         print "key = $key, value = $hash{$key}\n";
    }
}

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Or am I missing something?

HTH

Update: I forgot about the "modify hash" requirement - sorry. merlyn came up with a great one-liner, of course!

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Re^2: Selecting particular key-value pairs in hashes
by kiat (Vicar) on Sep 18, 2004 at 03:02 UTC
    Thanks, bobf!

    That was what I was going to do. But if I had proportionately more unwanted key-value pairs, the looping of keys to get to the right key-value pair might become an expensive operation.

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Re^2: Selecting particular key-value pairs in hashes
by Aristotle (Chancellor) on Sep 18, 2004 at 22:00 UTC

    Or some iterative versions which do a little less work:

    # destructive
while( my $k = each %hash ) {
    delete $hash{ $k } unless $k =~ /\d+_\d+/;
}

# nondestructive
my %hash2;
while( my( $k, $v ) = each %hash ) {
    $hash2{ $k } = $v if $k =~ /\d+_\d+/;
}

    [download]
    or maybe 
    # destructive
/\d+_\d+/ or delete $hash{ $_ } while local $_ = each %hash;

# nondestructive
my %hash2;
/\d+_\d+/ and $hash2{ $_ } = $a while local( $_, $a ) = each %hash;

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    Makeshifts last the longest.

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