diff --git a/scripts/runner.pl b/scripts/runner.pl
index c33bde6..b0f76dd 100644
--- a/scripts/runner.pl
+++ b/scripts/runner.pl
@@ -289,15 +289,15 @@ sub inject {
 }
 
 sub query {
-    my ( $experiment, $query, $args, $file, $substitution ) = @_;
+    my ( $experiment, $query, $args, $file, $postprocess ) = @_;
 
     say "Running query $query";
 
     my $result = qx{mariadb --defaults-file=$remote_db_conf $args -e "$query"};
     die "Query failed: $?" if $? != 0;
 
-    if ( defined $substitution ) {
-        $result =~ $substitution;
+    if ( defined $postprocess ) {
+        $postprocess->($result);
     }
 
     open( my $results_handle, '>', "$remote_builds_dir/$experiment/$file" )
@@ -339,7 +339,7 @@ GROUP BY p.injection_instr_absolute
 ORDER BY SUM(t.time2 - t.time1 + 1) DESC;";
 
     query( $experiment, $fail_markers_query, "--batch --raw",
-        "markers.csv", s/\t/,/g );
+        "markers.csv", sub { $_[0] =~ s/\t/,/g } );
 }
 
 # Run experiments