cat lill01.txt  

camel   42
pearl   94
dromedary       69

cat lill02.txt

camel   8
hello   12345
dromedary       1
perl    94

perl -lane "$r{$F[0]}+=$F[1]}{print qq($_\t$r{$_})for sort{$r{$b}<=>$r{$a}||$a cmp $b}keys %r" lill01.txt lill02.txt

# or shortened by one char because perl -a implies -n

perl -lae "$r{$F[0]}+=$F[1]}{print qq($_\t$r{$_})for sort{$r{$b}<=>$r{$a}||$a cmp $b}keys %r" lill01.txt lill02.txt

hello   12345
pearl   94
perl    94
dromedary       70
camel   50

##</code><code>##

perl -MO=Deparse -lane "$r{$F[0]}+=$F[1]}{print qq($_\t$r{$_})for sort{$r{$b}<=>$r{$a}||$a cmp $b}keys %r"

BEGIN { $/ = "\n"; $\ = "\n"; }                   # provided by: perl -l
LINE: while (defined($_ = readline ARGV)) {       # provided by: perl -n (cycling files in a loop but Not printing lines)
    chomp $_;                                     # also provided by: perl -l
    our @F = split(' ', $_, 0);                   # provided by: perl -a for Auotosplit, it puts stuff into @F automatically
    $r{$F[0]} += $F[1];
}                                                 # eskimo greeting..
{                                                 # ..see perlsecret
    print "$_\t$r{$_}" foreach (sort {$a cmp $b unless $r{$b} <=> $r{$a};} keys %r);
}
-e syntax OK