diff --git a/test_regress/driver.pl b/test_regress/driver.pl
index eadd21b69..6367b69bd 100755
--- a/test_regress/driver.pl
+++ b/test_regress/driver.pl
@@ -2079,6 +2079,7 @@ sub files_identical {
                     && !/^-node:/
                     && !/^dot [^\n]+\n/
                     && !/^In file: .*\/sc_.*:\d+/
+                    && !/^libgcov.*/
             } @l1;
             @l1 = map {
                 s/(Internal Error: [^\n]+\.cpp):[0-9]+:/$1:#:/;
@@ -2318,6 +2319,21 @@ sub write_wholefile {
     my $fh = IO::File->new(">$filename") or die "%Error: $! writing $filename,";
     print $fh $contents;
     $fh->close;
+    delete $_File_Contents_Cache{$filename};
+}
+
+sub file_sed {
+    my $self = (ref $_[0]? shift : $Self);
+    my $infilename = shift;
+    my $outfilename = shift;
+    my $editcb = shift;
+    my $contents = $self->file_contents($infilename);
+    {
+        $_ = $contents;
+        $editcb->($contents);
+        $contents = $_;
+    }
+    $self->write_wholefile($outfilename, $contents);
 }
 
 #######################################################################
diff --git a/test_regress/t/t_savable_format2_bad.pl b/test_regress/t/t_savable_format2_bad.pl
index c87d9cc87..8a6e75248 100755
--- a/test_regress/t/t_savable_format2_bad.pl
+++ b/test_regress/t/t_savable_format2_bad.pl
@@ -25,7 +25,9 @@ execute(
 -r "$Self->{obj_dir}/saved.vltsv" or error("Saved.vltsv not created\n");
 
 # Break the header
-run(cmd => ["sed -i.bak 's/verilatorsave01/verilatorsavBAD/' $Self->{obj_dir}/saved.vltsv"]);
+file_sed("$Self->{obj_dir}/saved.vltsv",
+         "$Self->{obj_dir}/saved.vltsv",
+         sub { s/verilatorsave01/verilatorsavBAD/g; });
 
 execute(
     all_run_flags => ['+save_restore=1'],
diff --git a/test_regress/t/t_savable_format3_bad.pl b/test_regress/t/t_savable_format3_bad.pl
index a0cc865de..ce78e55f1 100755
--- a/test_regress/t/t_savable_format3_bad.pl
+++ b/test_regress/t/t_savable_format3_bad.pl
@@ -25,7 +25,9 @@ execute(
 -r "$Self->{obj_dir}/saved.vltsv" or error("Saved.vltsv not created\n");
 
 # Break the header
-run(cmd => ["sed -i.bak 's/vltsaved/vltNOTed/' $Self->{obj_dir}/saved.vltsv"]);
+file_sed("$Self->{obj_dir}/saved.vltsv",
+         "$Self->{obj_dir}/saved.vltsv",
+         sub { s/vltsaved/vltNOTed/g; });
 
 execute(
     all_run_flags => ['+save_restore=1'],
diff --git a/test_regress/t/t_waiveroutput.pl b/test_regress/t/t_waiveroutput.pl
index 08f77ed08..9559ffed7 100755
--- a/test_regress/t/t_waiveroutput.pl
+++ b/test_regress/t/t_waiveroutput.pl
@@ -20,7 +20,8 @@ compile(
 
 files_identical("$out_filename", $Self->{golden_filename});
 
-run(cmd=>["sed 's/\\/\\/ lint_off/lint_off/g' $out_filename > $waiver_filename"]);
+file_sed($out_filename, $waiver_filename,
+         sub { s/\/\/ lint_off/lint_off/g; });
 
 compile(
     v_flags2 => [$waiver_filename],