[Koha] regex to put space between the classification number and author letters

[Lauren Denny]

Hi everyone,

I have about 5000 records with no space between the classification number
and author letters.  Here are a few examples:
491.431SA
431PA
260RE

I would like to add a space so that they become:
491.431 SA
431 PA
260 RE

Is there a way to add the space in the call number using the Koha item
batch modification?  I feel like I could use regex to add a space after the
numbers or before the letters but don't know enough about regex to know how.

Could someone help? Or offer another way to edit them?

Thanks,
Lauren