use strict;
use warnings;

my @d; # the data structure we're building.

my @p; # current (actually previous) vector

while (<DATA>)
{
	chomp;
	my $r = \@d;
	my @vc = my @v = split m# / #;
	my @pc = @p; # bashable copy
	while ( @vc and @pc and $vc[0] eq $pc[0] )
	{
		shift @vc; shift @pc;
		$r = $r->[-1]{'children'};
	}
	while ( @vc )
	{
		push @$r, { name => shift @vc };
		$r = ( @vc and $r->[-1]{'children'} = [] );
	}
	@p = @v;
}

use Data::Dumper;
print Dumper \@d;

__DATA__
one
foo / bar
foo / baz
foo / qux / two
foo / qux / three
foo / qux / four
five