perl -e 'while (<>){@a=split;$s{$a[0]}+=$a[1] if $a[1]}print "$_=$s{$_
+}$/"for sort keys %s' texto.txt


[fpalacios@linuxtest fpalacios]$ cat texto.txt
12345   99
12345   99
23432   99
54567   20
[fpalacios@linuxtest fpalacios]$ perl -e 'while (<>){@a=split;$s{$a[0]
+}+=$a[1] if $a[1]}print "$_=$s{$_}$/"for sort keys %s' texto.txt
12345=198
23432=99
54567=20
[fpalacios@linuxtest fpalacios]$
[download]

$_=$,=q,\,@4O,,s,^$,$\,,s,s,^,b9,s,
$_^=q,$\^-]!,,print
[download]