I offer a slight modification:

if (join('','a'..'m') =~ qr/$sv/ && $sv =~/^[a-m]{5}$/){
    print "Matched\n";
}
[download]

Which just means you don't need to specify the whole of the range, just the start and end, you could sub it like this:

sub match_range {
    my ($string, $start, $end, $length) = @_;
    if (join('',$start .. $end) !~ qr/$string/) { return 0; }
    if ($string !~ /^[${start}-${end}]{$length}$/) { return 0; }
    return 1;
}
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Nice, but since boolean operators shortcircuit anyway (ie the right operand of && won't even be evaluated if the left one is already false), you just added a lot of blocks for no gain. Also, return 0 is a bad meme, if you want to return false then just return (which is equivalent to return wantarray ? () : undef).

sub match_range {
    my ($string, $start, $end, $length) = @_;
    my $range = join '', $start .. $end;
    return
        $range =~ /$string/
        && $string =~ /^[$range]{$length}$/;
}
[download]

Just a bit of nitpickery.. :-)

Makeshifts last the longest.

Actually what I did was introduce two guard clauses. I am aware that it was correct in either fashion, it is my preference to have drop-through rules of the manner displayed previously. I also prefer explicit "false" return, and if there was some way I could say "return false" and get the same effect as just "return" I'd be using it :) undef isn't a bad concept tho.

Those are simply elements of my style however, the reasoning behind guard clauses is obvious in larger functions, in this case it is superfluous but assuming a reasonably efficient action on the part of the interpreter I see no likely efficiency loss, so the consistency rule applies :)

The re-use of the $range var is nice however.