Look at line 2147 of the data.
This could be a blank line?

Perhaps a regex is better?

#!/usr/bin/perl
use strict;
use warnings;
$|=1; #turn of buffering for STDERR


while (my $line = <DATA>)
{
   next unless $line =~ /\S/; #skip blank lines
   
   my ($label, $data) = $line =~ /\s*(\w+)\s*=\s*(\w+)/;
   die "bad line: $line" unless defined $data;
   
   print "label $label is: $data\n";
   
}

=prints
label a is: 3
label b is: 4
label c is: 55
label d is: 99
bad line: x=

Process completed with exit code 255

=cut


__DATA__
a = 3

b=4
  c = 55       
  d=99
x=
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