use strict;
use warnings;

my %ch;

while (<DATA>) {
    chomp;
    my ($logon, $ip) = split;
    $ch{"$logon -- $ip"}++;
}

foreach my $key (keys %ch) {print "$key -- $ch{$key}\n"};

__DATA__
xzc6548 192.168.10.5
xzc6548 192.168.10.5
xzc6548 192.168.10.10