in reply to Random hash element (low memory edition).

You could use something like this:

Code updated per ikegami's post below. 

sub getRandomPairFromHash{
    my $href = shift;
    my $nKeys = keys %$href;
    my $n = 1 + int rand $nKeys;
    my( $key, $val );
    ( $key, $val ) = each %$href while $n--;
    return ( $key, $val )
}

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It does work and doesn't increase the memory consumption, but fast it's not.

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Re^2: Random hash element (low memory edition).
by ikegami (Patriarch) on Jan 25, 2008 at 02:13 UTC

    That fails when $n == 0 and when $n == 1. One way to fix it is to apply both of the following changes:

    Change
    while --$n
    to
    while $n--

    Change
    my $n = int rand $nKeys;
    to
    my $n = 1 + int rand $nKeys;

    Update: Might as well post the modified code: 

    sub getRandomPairFromHash{
    my $href = shift;
    my $nKeys = keys %$href
       or return ( undef, undef );
    my $n = 1 + int rand $nKeys;
    my( $key, $val );
    ( $key, $val ) = each %$href while $n--;
    return ( $key, $val )
}

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