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The first line sets up a default interactive "gpaw-friendly" environment (killing any earlier environment settings!). You could use a similar line to pick up a default "jacapo-friendly" environment, if you prefer. The second line adds some necessary interactive commands (e.g. for submitting batch jobs).
If you want to pick up use a particular version (e.g. 27) of GPAW instead of the "default" above, use something like this instead:
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