my %juncture_of = (
    inm  => 'imm',  # immature
    abt  => 'abst', # abstract
    adt  => 'att',  # attempt
# etc.
);

sub join_euphoniously {
    my $compound = join '', @_;
    while ( my ($raw, $joined) = each %juncture_of ) {
        $compound =~ s/$raw/$joined/;
    }
    return $compound;
}

sub unjoin {
    my $compound = shift;
    
    # maybe no juncture rules applied to this one
    my @possibilities =  ( $compound );

    # analyze whether $string resulted from a juncture rule
    while (my ($raw, $joined) = each %juncture_of ) {
        for my $possibility (@possibilities) {
            if ( $possibility =~ s/$joined/$raw/ ) {
                push @possibilities, $possibility
            }
        }
    }
    return \@possibilities;
}