The presence of an unshift on line 9 is a syntax error as unshift requires a destination array which is not present in your example - I can only assume this is an artifact from a previous attempt involving a file slurp.

Why do you not want to insert "Date" on the first line of the file (unless clause of line 9, $.)? Particularly considering that it is a date, I would think that would be a desirable result.

Based on this code and the contents of insert label into file, perhaps you want something like this?

use strict;
use warnings;

my $text;

while(<DATA>) {
    chomp($_);
    if($_ =~ /\d{1,2}\/\d{1,2}\/\d{4}/) {
        $text .= "\nDate," unless $. == 1;
        $text .= $_;
    } else {
        $text .= ",\n".$_;
    }
}

print $text;

__DATA__
1/3/2007 12:20:01 AM
Login,12.588309
SearchLoad,9.432586
SearchCount,20:0.196329
SearchResults,7.418672
SearchSave,3.616305
SearchDelete,2.066482
SearchDetails,6.873061
ClientAdd,0.784989
CMALoad,1.859894
CMASave,3.249620
CMADelete,0.450952
ClientDelete,0.305768
Logout,0.823402
1/3/2007 12:49:22 AM
Login,10.958312
SearchLoad,13.644527
SearchCount,41:0.483233
SearchResults,7.027840
SearchSave,4.222601
SearchDelete,0.305821
SearchDetails,7.443877
ClientAdd,1.552915
CMALoad,1.202711
CMASave,5.285398
CMADelete,0.233119
ClientDelete,0.425521
Logout,0.560862
[download]

with output

1/3/2007 12:20:01 AM,
Login,12.588309,
SearchLoad,9.432586,
SearchCount,20:0.196329,
SearchResults,7.418672,
SearchSave,3.616305,
SearchDelete,2.066482,
SearchDetails,6.873061,
ClientAdd,0.784989,
CMALoad,1.859894,
CMASave,3.249620,
CMADelete,0.450952,
ClientDelete,0.305768,
Logout,0.823402
Date,1/3/2007 12:49:22 AM,
Login,10.958312,
SearchLoad,13.644527,
SearchCount,41:0.483233,
SearchResults,7.027840,
SearchSave,4.222601,
SearchDelete,0.305821,
SearchDetails,7.443877,
ClientAdd,1.552915,
CMALoad,1.202711,
CMASave,5.285398,
CMADelete,0.233119,
ClientDelete,0.425521,
Logout,0.560862
[download]