How about this way..

#!/usr/bin/perl -w
use strict;

while (<DATA>) {
    my @a = split(/\\/);
    print "$a[1] $a[2] $a[4]\n";

}

__DATA__
\nb\v5\srcccc\ans.cpp@@\main\
\nb\v5\srcccc\ans.cpp@@\main\
\nb\v5\srcccc\test.cpp@@\main\
\nb\v5\safe\test.cpp@@\main\
\nb\v5\safe\test.cpp@@\main\
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