use strict;
use warnings;

my @dirs;
while (<DATA>) {
    chomp;
    push @dirs, $_;
}

my %parents;
for my $dir1 (@dirs) {
    for my $dir (@dirs) {
        if (index($dir1, $dir) == 0) {
            # $dir1 is a substring of $dir, starting at pos 0
            $parents{$dir}++;
        }
    }
}

for (keys %parents) { print "$_\n" if $parents{$_} == 1 }

__DATA__
/tmp/a
/tmp/a/b
/tmp/a/b/c
/tmp/a/b/c/e
/tmp/a/b/d
/tmp/a/b/d/g
/tmp/a/b/d/g/h
/tmp/a/b/d/g/i
/tmp/a/b/k