How do I find the line number of a certain phrase in perl?

I am using a while loop to assign real numbers from an input file to an array. The input file is set up in a way that makes the first 21 points in the array blank. The number 21 corresponds to the line number containing the phrase "Range1" in my input file minus 1. I am using

splice @range_min, 0, $header_lines-1;

to remove those blank lines from my array.

I want $header_lines to be equal to the line number containing that phrase since I could potentially have other input files with that phrase on a different line.

I have already tried putting the following command into my while loop:

$header_lines = $., last if /Range1/;

which does work but it completely clears my array (defeating the purpose of my program).

Is there a better way to find the line number of my phrase in an input file without affecting my while loop or array?

Solution

Try putting this in your loop instead:

    if ( /Range1/ ) {
        $header_lines = $.;
    }

I think what's currently happening is that everytime through the loop, you are setting $header_lines to the current line number ($.). The code "last if /Range1/;" quits out of your loop when $_ matches Range1. So you would only be setting the first 21 lines, and then quitting, and then erasing all the lines.