numbering plan collapse ranges

#/usr/bin/perl
<>;
$prev_from="";
$prev_to="";
$prev_oper="";
while(<>){
    @l=split/,/;
    $from=shift @l;
    $to=shift @l;
    $oper=shift @l;

    #print "$from - $to = $oper\n";
    if(($prev_oper eq $oper) && ( ($prev_to+1)==($from+0) )) {
        #print "Joinable $prev_to and $from for $oper\n";
        $prev_to = $to;
    } else {
        print "$prev_from,$prev_to,$prev_oper\n";
        $prev_from = $from;
        $prev_to = $to;
        $prev_oper = $oper;
    }
}
print "$prev_from,$prev_to,$prev_oper\n";