$ perl -le ' > $str = q{YYSFTVMETDPVN[115]HMVGVISVEGRPGLFWFN[115]ISGGDKN[115]}; > @chunks = split m{(?<=N)\[115\]}, $str, -1; > $posn = -1; > print $posn += length for @chunks[ 0 .. $#chunks - 1 ];' 12 30 37 $