#! perl -slw
use strict;

my %hash = (
    MEX1J => {
        desc => 'Job 2',
        pred => [ 'TEX1J' ],
    },
    MEX2J => {
        desc => 'Job end',
        pred => [ qw[TEX1J MEX1J] ],
    },
    TEX1J => {
        desc => 'Job start',
        pred => [],
    }
);

my @orderedKeys = sort{ 
    return 0 unless @{ $hash{ $a }{ pred } }
                 or @{ $hash{ $b }{ pred } };

    my $AinB = grep /$a/, @{ $hash{ $b }{ pred } };
    my $BinA = grep /$b/, @{ $hash{ $a }{ pred } };
    die "Circular dependacy $a:$b" if $AinB and $BinA;

    return -1 if $AinB;
    return  1 if $BinA;
    return 0 unless $AinB or $BinA;
} keys %hash;

print "$_ $hash{ $_ }{ desc } @{ $hash{ $_ }{ pred } }"
    for @orderedKeys;

__END__
P:\test>500240
TEX1J Job start
MEX1J Job 2 TEX1J
MEX2J Job end TEX1J MEX1J


##</code><code>##

#! perl -slw
use strict;
use List::Util qw[first];

my %hash = (
    MEX1J => {
        desc => 'Job 2',
        pred => [ 'TEX1J' ],
    },
    MEX2J => {
        desc => 'Job end',
        pred => [ qw[TEX1J MEX1J] ],
    },
    TEX1J => {
        desc => 'Job start',
        pred => [],
    }
);

my %cache;
my @orderedKeys = sort{
    return 0 unless @{ $hash{ $a }{ pred } }
                 or @{ $hash{ $b }{ pred } };

    my $AinB = $cache{ "$a|$b" } ||= first{ /$a/ } @{ $hash{ $b }{ pred } };
    my $BinA = $cache{ "$b|$a" } ||= first{ /$b/ } @{ $hash{ $a }{ pred } };
    die "Circular dependacy $a:$b" if $AinB and $BinA;
    
    return -1 if $AinB;
    return  1 if $BinA;
    return 0 unless $AinB or $BinA;
} keys %hash;

print "$_ $hash{ $_ }{ desc } @{ $hash{ $_ }{ pred } }"
    for @orderedKeys;

__END__
P:\test>500240
TEX1J Job start
MEX1J Job 2 TEX1J
MEX2J Job end TEX1J MEX1J