c:\test>904729-3 >nul
Took 0.04846
2,4,4-Trimethyl-1-pentanol
        ->2,4,4-Trimethylpentanal
        ->2,4,4-Trimethylpentanoate
        ->2,4,4-Trimethylpentanoyl-CoA
        ->2,4,4-Trimethylpent-2-enoyl-CoA
        ->2,4,4-Trimethyl-3-hydroxypentanoyl-CoA
        ->2,4,4-Trimethyl-3-oxopentanoyl-CoA
        ->2,4,4-Trimethyl-3-oxopentanoate
        ->2,2-Dimethyl-3-pentanone
        ->1-Hydroxy-4,4-dimethylpentan-3-one
        ->4,4-Dimethyl-3-oxopentanal
2,4,4-Trimethyl-1-pentanol
        ->2,4,4-Trimethylpentanal
        ->2,4,4-Trimethylpentanoate
        ->2,4,4-Trimethylpentanoyl-CoA
        ->2,4,4-Trimethylpent-2-enoyl-CoA
        ->2,4,4-Trimethyl-3-hydroxypentanoyl-CoA
        ->2,4,4-Trimethyl-3-oxopentanoyl-CoA
        ->Pivalyl-CoA
2,4,4-Trimethyl-1-pentanol
        ->2,4,4-Trimethylpentanal
        ->2,4,4-Trimethylpentanoate
        ->2,4,4-Trimethylpentanoyl-CoA
        ->2,4,4-Trimethylpent-2-enoyl-CoA
        ->2,4,4-Trimethyl-3-hydroxypentanoyl-CoA
        ->2,4,4-Trimethyl-3-oxopentanoyl-CoA
        ->Propanoyl-CoA


##</code><code>##

#! perl -slw
use strict;
use Data::Dump qw[ pp ];
use List::Util qw[ shuffle ];
use Time::HiRes qw[ time ];

sub _pathsFrom2 {
    use enum qw[ CODE GRAPH START PATH SEEN ];

    return $_[CODE]->( @{ $_[PATH] }, $_[START] )
        unless exists $_[GRAPH]->{ $_[START] };

    for ( @{ $_[GRAPH]->{ $_[START] } } ) {
        if( exists $_[SEEN]->{ $_[START] . "-$_" } ) {
            return $_[CODE]->( @{ $_[PATH] }, $_[START] );
        }
        else {
            _pathsFrom2(
                @_[ CODE, GRAPH ], $_,
                [ @{ $_[PATH] }, $_[START] ], 
                { %{ $_[SEEN] }, $_[START] . "-$_", undef }
            );
        }
    }
}
sub pathsFrom2(&@) { _pathsFrom2( @_, [], {} ) }

my %graph;

<DATA>;

while( <DATA> ) {
    chomp;
    my @fields = split '\s{2,}';
    push @{ $graph{ $fields[0] } }, $fields[ 2 ];
}

my $start = time;

my @best = ( 0, 0 );
for my $start ( keys %graph ) {
    pathsFrom2{
        @best = ( scalar @_, $start ) if scalar @_ > $best[ 0 ];
        print join "\n\t->", @_;
    } \%graph, $start;
}

printf STDERR "Took %.5f\n", time() - $start;

pathsFrom2{
    print STDERR join "\n\t->", @_;
} \%graph, $best[ 1 ];


__DATA__
Substrate    Enzyme    Product
(-)-(1R,2S,5R)-Menthol    menthol dehydrogenase    (-)-(2S,5R)-Menthone
(-)-(2S,5R)-Menthone    menthone dehydrogenase    (5R)-Menth-2-enone
(+)-(3S,4R)-cis-3,4-Dihydroxy-3,4-dihydrofluorene    3,4-dihydroxy-3,4-dihydrofluorene dehydrogenase    3,4-Dihydroxyfluorene
(+)-(4R)-Limonene    limonene 1,2-monooxygenase    (4R)-Limonene-1,2-epoxide
(+)-Camphor    camphor 5-monooxygenase    5-exo-Hydroxycamphor
(+)-cis-3,4-Dihydrophenanthrene-3,4-diol     cis-3,4-dihydrophenanthrene-3,4-diol dehydrogenase    Phenanthrene-3,4-diol
(1-Methylpentyl)succinate    succinyl-CoA transferase    (1-Methylpentyl)succinyl-CoA
(1-Methylpentyl)succinyl-CoA    methylmalonyl-CoA mutase    (2-Methylhexyl)malonyl-CoA
(1R)-Glutathionyl-(2R)-hydroxy-1,2-dihydronaphthalene    No Kegg enzyme supplied    (1R)-N-Acetyl-L-cysteinyl-(2R)-hydroxy-1,2-dihydronaphthalene
(1R)-Glutathionyl-(2R)-hydroxy-1,2-dihydronaphthalene    No Kegg enzyme supplied    (1R,2R)-3-[(1,2-Dihydro-2-hydroxy-1-naphthalenyl)thio]-2-oxopropanoic acid
(1R)-Hydroxy-(2R)-glutathionyl-1,2-dihydronaphthalene    No Kegg enzyme supplied    (1R)-Hydroxy-(2R)-N-acetyl-L-cysteinyl-1,2-dihydronaphthalene
...