$filename =~ s/\/[\/]+/\//;

##</code><code>##

#  Used a delimiter other than '/' to avoid escaping '/'.
$p =~ s!//+!/!g;

##</code><code>##

$p = '/vobs/synergy_core_apps/code/../code/personalize/src';

print 'before: ' , $p , "\n";

#  Besides the /g flag, used /x in order to make the pattern stand out.
$p =~ s{ ([^/]+) /[.]{2}/ \1 } /$1/gx;

print 'after: ' , $p , "\n";