Integers in list not appearing in output when processing with explode

I'm using explode to split a comma-separated list of items within an XML node and then use the results as taxonomy terms. I'm finding that if the list contains integers these are not appearing in the output. Details as follows.

When using explode on a list like this:

<some-element>123,1.23,abc,456 ,789,def890</some-element>

I get back (in the field to which the node is mapped):

1.23, abc, 456, def890 as the exploded values.

123 and 789 are not processed

Looks as though values which could be interpreted as integers are not being output.

In the example the trailing space after 456 ensures that it is output whereas 123 and 789 go awol. I've worked around the issue by ensuring that all comma-separated items are also followed by a trailing space.