use strict;
use warnings;
use Data::Dumper;

my %hash;

while ( <DATA> ) {
    chomp;
    my @vals = split ':';
    if ( scalar( @vals ) % 2 ) {
        @{ $hash{$vals[0]} }{ @vals[1..($#vals/2)] } = @vals[( ($#vals/2)+1 )..$#vals];
    } else {
        print "Uneven number of elements: $_\n";
    }
}
print Dumper %hash;
__DATA__
users:john:mary:1:2
cities:Portland:Amsterdam:New York:Pretty Cool:Awesome:Ugh!
misc:foo:bar:baz:Ovid