Hi Anonymous,

Have a look at "hashes of hashes" in perldsc, for example:

use warnings;
use strict;

my @routers = ( "R1", "R2", "R3" );
my %if = (
    R1 => { R1R0  => 1, R1R6  => 2, },
    R2 => { R2R0  => 3, R2R6  => 1, },
    R3 => { R3R61 => 2, R3R62 => 3, },
);

for my $r (@routers) {
    for my $i (keys %{ $if{$r} }) {
        print "Router $r Interface $i\n";
    }
}

__END__

Router R1 Interface R1R0
Router R1 Interface R1R6
Router R2 Interface R2R0
Router R2 Interface R2R6
Router R3 Interface R3R61
Router R3 Interface R3R62
[download]

Alternatively, if you're stuck with the structure of the %interfaces hash, and the keys are always named beginning with the router's ID, you could use grep:

use warnings;
use strict;

my @routers = ( "R1", "R2", "R3" );
my %interfaces =  (
    R1R0  => 1, R1R6  => 2,
    R2R0  => 3, R2R6  => 1,
    R3R61 => 2, R3R62 => 3,
);

for my $r (@routers) {
    my @ifs = grep {/^\Q$r\E\D/} keys %interfaces;
    for my $i (@ifs) {
        print "Router $r Interface $i\n";
    }
}
[download]

Hope this helps,
-- Hauke D