If you step through the array backward, you can delete (splice) out the redundant elements safely.

This will do it, but the code doesn't format nicely:

#! perl -slw
use strict;
use Data::Dump qw[ pp ];

my @a = map[ split ], <DATA>;

substr( $a[$_-1][0],0,-1 ) eq substr( $a[$_][0],0,-1 )
    and do{ $a[$_-1][1] += $a[$_][1]; splice @a, $_, 1; }
    for reverse 1 .. $#a;

pp \@a;

__DATA__
19.25.55.11.144.0      5
19.25.55.14.16.0      12
19.25.59.200.208.0      8
19.25.59.204.160.0      7
19.25.60.5.176.0      4
19.25.60.15.48.0      0
19.25.60.17.240.0      3
19.25.60.18.96.0      5
19.25.115.138.224.0      30
19.25.115.141.32.0      4
26.109.108.64.144.0      1
38.153.162.89.0.0      1
38.153.162.89.0.1      0
38.153.162.89.96.0      0
38.153.162.89.96.1      0
38.153.162.95.64.0      0
38.153.162.95.64.1      0
58.152.64.24.192.0      1
58.152.64.24.192.1      0
58.152.64.46.48.0      3
58.152.64.46.48.1      0
58.152.94.71.0.0      1
58.152.94.71.0.1      0
[download]

Output:

C:\test>junk
[
  ["19.25.55.11.144.0", 5],
  ["19.25.55.14.16.0", 12],
  ["19.25.59.200.208.0", 8],
  ["19.25.59.204.160.0", 7],
  ["19.25.60.5.176.0", 4],
  ["19.25.60.15.48.0", 0],
  ["19.25.60.17.240.0", 3],
  ["19.25.60.18.96.0", 5],
  ["19.25.115.138.224.0", 30],
  ["19.25.115.141.32.0", 4],
  ["26.109.108.64.144.0", 1],
  ["38.153.162.89.0.0", 1],
  ["38.153.162.89.96.0", 0],
  ["38.153.162.95.64.0", 0],
  ["58.152.64.24.192.0", 1],
  ["58.152.64.46.48.0", 3],
  ["58.152.94.71.0.0", 1],
]
[download]