use strict;
use warnings;
#define a regexp matching the interesting variable names
my $interesting_vars = 
  qr(a111111111111111111111111|c222222222222222222222222);
#sample input rows
my @rows = ('a111111111111111111111111              1b8888888888888888888888888            15x222222222222222222222222              2', 
            'd999999999999999999999999              4b3333333333333333333333333            15c222222222222222222222222            123');

for (@rows) {
  #split by variable value pairs  
  for (/.{40}/g) {
    #split variable and value
    /(.{25})(.{15})/;
    #since I am doing an additional match, I have to
    #save my submatches
    my $var = $1;
    my $val = $2;
    print "'$var' = '$val'\n" 
      if $var =~ $interesting_vars;   
  }
}