Hi,
I have a hash with keys of the format
sar0011_4 sar0203_3 sar0050_5 sar2001_1 sar0002_9
And I would like to generate a list ordered by the \d\d\d\d bit in the middle. I have this from the perl cookbook
my @keys = sort {criterion()} keys(%gene_pool);
but I don't really know how to approach the criterion() function
In the case you show (where the first three characters are all 'sar'), you could simply sort on the entire key. I'll assume, however, that the prefix varies. Assuming, as well, that the length of the prefix is always three, you should be able to use:
<science fiction>
sub by_middle { substr($a, 3, 4) cmp substr($b, 3, 4) }
my @keys = sort by_middle keys(%gene_pool);
</science fiction>If the keys are less regular, you'll have to work harder to extract them.
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