Using next that way doesn't play with -p unfortunately. Ignoring that issue, here's a doozy to do the same: 
perl -l054p012e'($\,$a)=($a||$\,$b||$/);$b=$\'

[download]

:-)

Update:

$ perl -l054p012e'($\,$a)=($a||$\,$b||$/);$b=$\' <<EOT
> a
> b
> c
> d
> e
> f
> g
> h
> EOT
a,b
c,d
e,f
g,h

Makeshifts last the longest.

In reply to Re: Merge pairs of lines by Aristotle
in thread Merge pairs of lines by integral

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