git-svn: Don't rely on $_ after making a function call

git-svn: Don't rely on $_ after making a function call

Many functions and operators in perl set $_, so its value cannot be relied upon
after calling arbitrary functions. The solution is simply to copy the value of
$_ into a local variable that will not get overwritten.

Signed-off-by: Adam Roben <aroben@apple.com>
Acked-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>