The data is being generated as part of a backup process, whose naming is outside my control. I have to collate stats on the various backup folders, by a derived group name.

If I were to hand code it, I would do something like:

use File::Basename qw( dirname basename );

for my $folder (
   '/var/vavoom/cherry/cherry_etc',         # cherry_etc
   '/var/varoom/cherry/cherry_var_data',    # cherry_var_data
   '/var/vavoom/peach/peach_etc',           # peach_etc
   '/var/varoom/mysql/peach_mysql_chant',   # mysql_peach_chant
   '/var/vavoom/upload/var_finite',         # upload_var_finite
   '/var/vavoom/upload/var_open',           # upload_var_open
  ) {

    my $group   = basename($folder);
    my $parent  = basename(dirname($folder));
    $group =~ s/$parent\_//g;
    $group =  $parent . '_' . $group;
    print sprintf("%-40s %s\n", $folder, $group );
}

/var/vavoom/cherry/cherry_etc            cherry_etc
/var/varoom/cherry/cherry_var_data       cherry_var_data
/var/vavoom/peach/peach_etc              peach_etc
/var/varoom/mysql/peach_mysql_chant      mysql_peach_chant
/var/vavoom/upload/var_finite            upload_var_finite
/var/vavoom/upload/var_open              upload_var_open
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I was hoping for pointers to an RE technique that would enable me to consolidate repeating words.