Indeed.

There are a number of ways to preserve the order. Here's a slightly whimsical one:

my $string = "1:1,2:1,3:2,500:2,505:1";
my %hash = split /[:,]/, $string;
my @array = split /:.+?,?/, $string;          #  :-)
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or another:

my $string = "1:1,2:1,3:2,500:2,505:1";
my %hash = my @array = split /[:,]/, $string;
@array = @array[grep $_%2==0, 0..$#array];
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But these probably drive the original split idea far far into the ground :-)