Using printf within the substitution:

#! perl
use strict;
use warnings;

while (<DATA>)
{
    chomp;
    s[\s(\d+)\d\K\s(?=(\d+)\d\s)]
    {
        printf("%s: (%s) (%s)\n", $_, $1, $2);
    }ge;
}

__DATA__
105 106 107 108 109 110 111 112 113
1115 1116 1117 1118 1119 1120 1121 1122 1123
12345 12346 12347 12348 12349 12350 12351 12353
[download]

gives:

20:32 >perl 687_SoPW.pl
105 106 107 108 109 110 111 112 113: (10) (10)
105 106 107 108 109 110 111 112 113: (10) (10)
105 106 107 108 109 110 111 112 113: (11) (11)
1115 1116 1117 1118 1119 1120 1121 1122 1123: (111) (111)
1115 1116 1117 1118 1119 1120 1121 1122 1123: (111) (111)
1115 1116 1117 1118 1119 1120 1121 1122 1123: (112) (112)
12345 12346 12347 12348 12349 12350 12351 12353: (1234) (1234)
12345 12346 12347 12348 12349 12350 12351 12353: (1234) (1234)
12345 12346 12347 12348 12349 12350 12351 12353: (1235) (1235)

20:32 >
[download]

which seems to show that each comparison is consuming three terms from the data line, instead of one. I don’t understand why this is, but I’m posting in the hope that it provides someone with a useful clue as to what is going on. :-)