use v5.12; use warnings; use Test::More; my $str = '43:1:1; 43:1:2; 43:1:3; 43:1:4; 43:1:5; 43:1:6; 27:3:7; 27:3:8; 27:3:9; 65:1:4; 65:1:18'; my $exp = '43:1:1-6; 27:3:7-9; 65:1:4; 65:1:18'; my $got = $str; $got =~ s/ ( \d+:\d+: ) # $1 ( \d+ # (updated +) ) # $2 = first $^N ; (?: # group w/o match \s \1 ( (??{ $^N+ 1 }) # include last_match + 1 ) # $3 = next $^N ; )+ # repeat /$1$2-$3;/xg; is($got, $exp, "fits"); done_testing;