As chromatic said you need two separate loops , one for each column

#!/usr/bin/perl
use strict;
use Spreadsheet::XLSX;

my $excel = Spreadsheet::XLSX -> new ('build.xlsx');
my $sheet = $excel->Worksheet('Sheet1');
my ($row_min,$row_max) = $sheet->row_range();

# scan col D and store values
my %colD=();
for my $row ($row_min..$row_max){
  my $valD = $sheet->{Cells}[$row][3]->{Val}; 
  $colD{$valD} = $row+1; # excel row number
}

# scan col A starting at row 2
open FILE,'>','feckyou.txt' or die $!;
for my $row (1..$row_max){
  my $valA = $sheet->{Cells}[$row][0]->{Val};
  # does this value exist in Col D
  if (exists $colD{$valA}) {
    my $xlrow = $row+1;
    print FILE "price change [A$xlrow]=[D$colD{$valA}] Value=$valA\n";
  }
}
[download]

poj