in reply to passing bits of an array to an executable a piece at a time

Whether this i sthe best way of doing this is an open question, but to pass your array in 200 element chucks, you could use splice. I'm assuming that select_ids() returns a reference to an array.

launch_background( 'glim.exe', 'glim', join' ', splice( @$ids, 0, 200 ); ) while @$ids;

This will consume the array. If you need to retain the array then make a copy. If the array is big and copying costs too much memory then you would need to use a slice and a pointer.

launch_background( 'glim.exe', 'glim', join' ', @{ $ids }[ $_ .. ( $_ + 200 ) ] ) for map $_ * 200, 0 .. int( @$ids / 200 );

You will probably need to add a little logic to the calculation of the upper bound of the slice to prevent "Uninitialised values" warnings unless your array is a multiple of 200.

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