42 
                          123456789          2         3         4
% cat data.output | perl -p0e'/(\d+\.\d+).*(\d+\.\d+)/s;$_=$2-$1.$:'

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I added a closing CR because output doesn't display otherwise (at least not for my install :) - without it, it's 39

cLive ;-)

update - as chipmunk points out, this fails. In my effort to fp a reply, I missed out the : , ie: 

% cat data.output | perl -p0e'/(\d+\.\d+).*:(\d+\.\d+)/s;$_=$2-$1.$:'

[download]
Shame on y'all who ++d my reply :)

In reply to (cLive ;-)(Golf) Analyzing Time From tcpdump Output by cLive ;-)
in thread (Golf) Analyzing Time From tcpdump Output by enoch

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