I forgot about the special behaviour of .. in scalar context, when the operands are literal integers. In that case, that value is automatically compared against $.. So my code can be simplified to: 
open IN, "<", $file or die "Can't open file $file: $!";
my %data;
while(<IN>) {
    if(1 .. 2) {
        my($number) = /([\d.]+)\s*$/;
        $data{$.} = $number;
    }
}

[download]

If you need several distinct ranges, you can do 

if(1 .. 2 or 6 .. 8) {

[download]
as can be demonstrated using the following code: 
while(<DATA>) {
    if(1 .. 2 or 6 .. 8) {
        print "$.: $_";
    }
}
__DATA__
one
two
three
four
five
six
seven
eight
nine
ten

[download]
Result: 
1: one
2: two
6: six
7: seven
8: eight
For a single value, you can choose between 4 == $. and 4 .. 4: 
if(1 .. 2 or 4 == $. or 6 .. 8) {

[download]
if(1 .. 2 or 4 .. 4 or 6 .. 8) {

[download]

In reply to Re^2: Matching on a specific line of text by bart
in thread Matching on a specific line of text by kingdom

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.