use List::Util qw( max );
use List::MoreUtils qw( mesh );

# Find the length of the longest list.
my $longest = max map { scalar @{ $_ } } @{ $foo };

# Pad every array to equal length using empty strings.
push @{ $_ }, ( q{} ) x ( $longest - scalar @{ $_ } ) for @{ $foo };

# Since 'mesh' takes a list of arrays, using a prototype,
# I use '&mesh' to avoid the prototype.
my @meshed = &mesh( @{ $foo } );

# Alternate way to do the same thing
#my @meshed = eval "mesh " . join q{,},
#             map { "\@{ \$foo->[ $_ ] }" } 0 .. $#{ $foo };

# Pull out the individual rows.
my $bar = [];
push @{ $bar }, [ splice @meshed, 0, $longest ] while @meshed;