my $string = '1,2,3,4,5:one,two,three,four,five';
my %results;
my @vals = split /[:,]/, $string;

if ( $#vals % 2 ) {
    for ( 0 .. int( $#vals/2 ) ) {
        $results{ $vals[ $_ ] } = $vals[ $_ + int( $#vals/2 ) + 1 ];
    }
}