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 $a[1]}print "$_=$s{$_}$/"for sort keys %s' texto.txt
12345=198
23432=99
54567=20
[fpalacios@linuxtest fpalacios]$